Functional assays that use the T1R2 taste receptor to identify potential taste modulators

ABSTRACT

Functional assays that use hT1R2 receptor polypeptides to screen for taste modulatory compounds are provided. In preferred embodiments these assays will use cells that stably or transiently express an hT1R2 polypeptide and which further express a suitable protein, e.g. G α15 , G α16  or gustducin. Such functional assays will screen for the effect of compound on T1R2 activity by detecting changes in cell voltage, intracellular ions, phosphorylation, second messenger levels and the like. Compounds identified in such assays are potentially useful as taste modulators. In preferred embodiments, the effect of selected compounds is evaluated further in human taste tests.

RELATED APPLICATIONS

[0001] This application claims benefit of priority to U.S. Serial No. 60/259,227 filed on Jan. 3, 2001 and U.S. Serial No. 60/284,547, filed on Apr. 19, 2001, both of which are incorporated by reference in their entirety herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to newly identified mammalian chemosensory G protein-coupled receptors, to family of such receptors, and to the genes and cDNA encoding said receptors. More particularly, the invention relates to newly identified mammalian chemosensory G protein-coupled receptors active in taste signaling, to a family of such receptors, to the genes and cDNA encoding said receptors, and to methods of using such receptors, genes, and cDNA in the analysis and discovery of taste modulators. The invention provides in particular a DNA sequence encoding a novel human taste receptor identified infra as T1R2 and the corresponding receptor polypeptide.

[0004] 2. Description of the Related Art

[0005] The taste system provides sensory information about the chemical composition of the external world. Mammals are believed to have at least five basic taste modalities: sweet, bitter, sour, salty, and umami. See, e.g., Kawamura et al., Introduction to Umami: A Basic Taste (1987); Kinnamon et al., Ann. Rev. Physiol., 54:715-31 (1992); Lindemann, Physiol. Rev., 76:718-66 (1996); Stewart et al., Am. J. Physiol., 272:1-26(1997). Each taste modality is thought to be mediated by a distinct protein receptor or receptors that are expressed in taste receptor cells on the surface of the tongue (Lindemann, Physol. Rev. 76:718-716 (1996)). The taste receptors that recognize bitter, sweet, and umami taste stimuli belong to the G-protein-coupled receptor (GPCR) superfamily (Hoon et al., Cell 96:451 (1999); Adler et al., Cell 100:693 (2000)). (Other taste modalities are believed to be mediated by ion channels.)

[0006] G protein-coupled receptors mediate many other physiological functions, such as endocrine function, exocrine function, heart rate, lipolysis, and carbohydrate metabolism. The biochemical analysis and molecular cloning of a number of such receptors has revealed many basic principles regarding the function of these receptors. For example, U.S. Pat. No. 5,691,188 describes how upon a ligand binding to a GPCR, the receptor undergoes a conformational change leading to activation of a heterotrimeric G protein by promoting the displacement of bound GDP by GTP on the surface of the Ga subunit and subsequent dissociation of the Ga subunit from the Gb and Gg subunits. The free Ga subunits and Gbg complexes activate downstream elements of a variety of signal transduction pathways.

[0007] Complete or partial sequences of numerous human and other eukaryotic chemosensory receptors are currently known. See, e.g., Pilpel, Y. and Lancet, D., Protein Science, 8:969-977 (1999); Mombaerts, P., Annu. Rev. Neurosci., 22:487-50 (1999). See also, EP0867508A2, U.S. Pat. No. 5,874,243, WO 92/17585, WO 95/18140, WO 97/17444, WO 99/67282. Because of the complexity of ligand-receptor interactions, and more particularly taste stimulus-receptor interactions, information about ligand-receptor recognition is lacking.

[0008] The identification and characterization of the GPCRs that function as sweet and umami taste receptors could allow for new methods of discovery of new taste stimuli. For example, the availability of receptors could permit the screening for receptor modulators. Such compounds would modulate taste and could be useful in the food industry to improve the taste of a variety of consumer products; e.g., improving the palatability of low-calorie beverages through the development of new artificial sweeteners.

[0009] In part, the present invention addresses the need for better understanding of the interactions between chemosensory receptors and chemical stimuli. The present invention also provides, among other things, novel chemosensory receptors, and methods for utilizing such receptors, and the genes a cDNAs encoding such receptors, to identify molecules that can be used to modulate chemosensory transduction, such as taste sensation.

SUMMARY OF THE INVENTION

[0010] The invention relates to a new family of G protein-coupled receptors, and to the genes and cDNAs encoding said receptors. The receptors are thought to be primarily involved in sweet taste transduction, but can be involved in transducing signals from other taste modalities as well.

[0011] The invention provides methods for representing the perception of taste and/or for predicting the perception of taste in a mammal, including in a human. Preferably, such methods may be performed by using the receptors and genes encoding said receptors disclosed herein.

[0012] Toward that end, it is an object of the invention to provide a new family of mammalian G protein-coupled receptors, herein referred to as T1Rs, active in taste perception. It is another object of the invention to provide fragments and variants of such T1Rs that retain taste stimulus-binding activity.

[0013] It is yet another object of the invention to provide nucleic acid sequences or molecules that encode such T1Rs, fragments, or variants thereof.

[0014] It is still another object of the invention to provide expression vectors which include nucleic acid sequences that encode such T1Rs, or fragments or variants thereof, which are operably linked to at least one regulatory sequence such as a promoter, enhancer, or other sequence involved in positive or negative gene transcription and/or translation.

[0015] It is still another object of the invention to provide human or non-human cells that functionally express at least one of such T1Rs, or fragments or variants thereof.

[0016] It is still another object of the invention to provide T1R fusion proteins or polypeptides which include at least a fragment of at least one of such T1Rs.

[0017] It is another object of the invention to provide an isolated nucleic acid molecule encoding a T1R polypeptide comprising a nucleic acid sequence that is at least 50%, preferably 75%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identical to a nucleic acid sequence selected from the group consisting of: SEQ ID NOS: 1, 2, 3, 9, 11, 13, 15, 16, 20, and conservatively modified variants thereof.

[0018] It is a further object of the invention to provide an isolated nucleic acid molecule comprising a nucleic acid sequence that encodes a polypeptide having an amino acid sequence at least 35 to 50%, and preferably 60%, 75%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identical to an amino acid sequence selected from the group consisting of: SEQ ID NOS: 4, 10, 12, 14, 17, 21, and conservatively modified variants thereof, wherein the fragment is at least 20, preferably 40, 60, 80, 100, 150, 200, or 250 amino acids in length. Optionally, the fragment can be an antigenic fragment which binds to an anti-T1R antibody.

[0019] It is still a further object of the invention to provide an isolated polypeptide comprising a variant of said fragment, wherein there is a variation in at most 10, preferably 5, 4, 3, 2, or 1 amino acid residues.

[0020] It is still another object of the invention to provide agonists or antagonists of such T1Rs, or fragments or variants thereof.

[0021] It is yet another object of the invention to provide methods for representing the perception of taste and/or for predicting the perception of taste in a mammal, including in a human. Preferably, such methods may be performed by using the T1Rs, or fragments or variants thereof, and genes encoding such T1Rs, or fragments or variants thereof, disclosed herein.

[0022] It is yet another object of the invention to provide novel molecules or combinations of molecules which elicit a predetermined taste perception in a mammal. Such molecules or compositions can be generated by determining a value of taste perception in a mammal for a known molecule or combinations of molecules; determining a value of taste perception in a mammal for one or more unknown molecules or combinations of molecules; comparing the value of taste perception in a mammal for one or more unknown compositions to the value of taste perception in a mammal for one or more known compositions; selecting a molecule or combination of molecules that elicits a predetermined taste perception in a mammal; and combining two or more unknown molecules or combinations of molecules to form a molecule or combination of molecules that elicits a predetermined taste perception in a mammal. The combining step yields a single molecule or a combination of molecules that elicits a predetermined taste perception in a mammal.

[0023] It is still a further object of the invention to provide a method of screening one or more compounds for the presence of a taste detectable by a mammal, comprising: a step of contacting said one or more compounds with at least one of the disclosed T1Rs, fragments or variants thereof, preferably wherein the mammal is a human.

[0024] It is another object of the invention to provided a method for simulating a taste, comprising the steps of: for each of a plurality of T1Rs, or fragments of variants thereof disclosed herein, preferably human T1Rs, ascertaining the extent to which the T1R interacts with the taste stimulus; and combining a plurality of compounds, each having a previously ascertained interaction with one or more of the T1Rs, in amounts that together provide a receptor-stimulation profile that mimics the profile for the taste. Interaction of a taste stimulus with a T1R can be determined using any of the binding or reporter assays described herein. The plurality of compounds may then be combined to form a mixture. If desired, one or more of the plurality of the compounds can be combined covalently. The combined compounds substantially stimulate at least 50%, 60%, 70%, 75%, 80% or 90% or all of the receptors that are substantially stimulated by the taste stimulus.

[0025] In yet another aspect of the invention, a method is provided wherein a plurality of standard compounds are tested against a plurality of T1Rs, or fragments or variants thereof, to ascertain the extent to which the T1Rs each interact with each standard compound, thereby generating a receptor stimulation profile for each standard compound. These receptor stimulation profiles may then be stored in a relational database on a data storage medium. The method may further comprise providing a desired receptor-stimulation profile for a taste; comparing the desired receptor stimulation profile to the relational database; and ascertaining one or more combinations of standard compounds that most closely match the desired receptor-stimulation profile. The method may further comprise combining standard compounds in one or more of the ascertained combinations to simulate the taste.

[0026] It is a further object of the invention to provide a method for representing taste perception of a particular taste stimulus in a mammal, comprising the steps of: providing values X₁ to X_(n) representative of the quantitative stimulation of each of n T1Rs of said vertebrate, where n is greater than or equal to 2; and generating from said values a quantitative representation of taste perception. The T1Rs may be an taste receptor disclosed herein, or fragments or variants thereof, the representation may constitutes a point or a volume in n-dimensional space, may constitutes a graph or a spectrum, and may constitutes a matrix of quantitative representations. Also, the providing step may comprise contacting a plurality of recombinantly-produced T1Rs, or fragments or variants thereof, with a test composition and quantitatively measuring the interaction of said composition with said receptors.

[0027] It is yet another object of the invention to provide a method for predicting the taste perception in a mammal generated by one or more molecules or combinations of molecules yielding unknown taste perception in a mammal, comprising the steps of: providing values X₁ to X_(n) representative of the quantitative stimulation of each of n T1Rs of said vertebrate, where n is greater than or equal to 2; for one or more molecules or combinations of molecules yielding known taste perception in a mammal; and generating from said values a quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding known taste perception in a mammal, providing values X₁ to X_(n) representative of the quantitative stimulation of each of n T1Rs of said vertebrate, where n is greater than or equal to 2; for one or more molecules or combinations of molecules yielding unknown taste perception in a mammal; and generating from said values a quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding unknown taste perception in a mammal, and predicting the taste perception in a mammal generated by one or more molecules or combinations of molecules yielding unknown taste perception in a mammal by comparing the quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding unknown taste perception in a mammal to the quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding known taste perception in a mammal. The T1Rs used in this method may include a taste receptor, or fragment or variant thereof, disclosed herein.

DETAILED DESCRIPTION OF THE FIGURES

[0028]FIGS. 1a-1 c present functional data for the human T1R2/T1R3 receptor. Intracellular calcium responses of HEK cells stably expressing Gα15 that are transiently transfected with human T1R2, T1R3, and T1R2/T1R3 to various concentrations of sucrose are shown in FIG. 1a. Each panel corresponds to approximately 1000 confluent, transfected, and calcium-dye-loaded cells. Inhibition of T1R2/T1R3 activity by the sweet-taste inhibitor gurmarin is shown in FIG. 1b. T1R2/T1R3 dose responses to four sweeteners and correlated psychophysical detection thresholds (X-axis circles) are shown in FIG. 1c.

[0029]FIG. 2 presents functional data for the rat T1R2/T1R3 receptor. Human T1R2/T1R3 and rat T1R2/T1R3 (as well as mixed rat/human receptors) responses to 350 mM sucrose, 25 mM tryptophan, 15 mM aspartame, and 0.05% monellin are shown. Rat T1R2/T1R3 does not respond to aspartame or monellin, which are not palatable to rodents.

[0030]FIGS. 3a-3 c present functional data for the human T1R2/T1R3 receptor. Intracellular calcium responses of HEK cells stably expressing Gal 5 that are transiently transfected with human T1R1, T1R3, and T1R1/T1R3 to various concentrations of L-glutamate are shown in FIG. 3a. Potentiation of the T1R1/T1R3 response by IMP is shown in FIG. 3b. T1R1/T1R3 dose responses to L-glutamate and L-glutamate plus 0.2 mM IMP and correlated psychophysical detection thresholds (X-axis circles) are shown in FIG. 3c.

[0031]FIGS. 4a-4 b present immunofluorescence and FACS experiments that demonstrate that fusing the PDZIP peptide (SEQ ID No:1) to human T1R2 enhanced its expression on the surface of HEK cells.

[0032]FIG. 5 presents automated fluorescence imaging data for cell lines that stably express Gα15 and human T1R1/T1R3. L-glutamate dose responses were determined in the presence of 0.5 mM IMP.

[0033]FIG. 6 presents automated fluorescence imaging data for cell lines that stably express Gal 5 and human T1R2/T1R3. Sucrose, D-tryptophan, saccharin, and aspartame dose responses are shown for on stable cell line.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The invention thus provides isolated nucleic acid molecules encoding taste-cell-specific G protein-coupled receptors (“GPCR”), and the polypeptides they encode. These nucleic acid molecules and the polypeptides that they encode are members of the T1R family of taste-cell-specific GPCRs. Members of the T1R family of taste-cell-specific GPCRs are identified in Hoon et al., Cell, 96:541-551 (1999), WO 00/06592, and WO 00/06593, all of which are incorporated herein by reference in their entireties.

[0035] More particularly, the invention provides nucleic acids encoding a novel family of taste-cell-specific GPCRs. These nucleic acids and the receptors that they encode are referred to as members of the “T1R” family of taste-cell-specific GPCRs. In particular embodiments of the invention, the T1R family members include human T1R1, T1R2, and T1R3. As described supra, different T1R combinations likely mediate sweet and umami taste.

[0036] Further, it is believed that T1R family members may act in combination with other T1R family members, other taste-cell-specific GPCRs, or a combination thereof, to thereby effect chemosensory taste transduction. For instance, it is believed that T1R1 and T1R3 maybe coexressed within the same taste receptor cell type, and the two receptors may physically interact to form a heterodimeric taste receptor. Alternatively, T1R1 and T1R3 may both independently bind to the same type of ligand, and their combined binding may result in a specific perceived taste sensation.

[0037] These nucleic acids provide valuable probes for the identification of taste cells, as the nucleic acids are specifically expressed in taste cells. For example, probes for T1R polypeptides and proteins can be used to identify taste cells present in foliate, circumvallate, and fungiform papillae, as well as taste cells present in the geschmackstreifen, oral cavity, gastrointestinal epithelium, and epiglottis. They may also serve as tools for the generation of taste topographic maps that elucidate the relationship between the taste cells of the tongue and taste sensory neurons leading to taste centers in the brain. In particular, methods of detecting T1Rs can be used to identify taste cells sensitive to sweet taste stimuli or other specific modalities of taste stimuli. Furthermore, the nucleic acids and the proteins they encode can be used as probes to dissect taste-induced behaviors. Also, chromosome localization of the genes encoding human T1Rs can be used to identify diseases, mutations, and traits caused by and associated with T1R family members.

[0038] The nucleic acids encoding the T1R proteins and polypeptides of the invention can be isolated from a variety of sources, genetically engineered, amplified, synthesized, and/or expressed recombinantly according to the methods disclosed in WO 00/035,374, which is herein incorporated by reference in its entirety.

[0039] The invention also provides methods of screening for modulators, e.g., activators, inhibitors, stimulators, enhancers, agonists, and antagonists, of these novel taste-cell-specific GPCRs. Such modulators of taste transduction are useful for pharmacological, chemical, and genetic modulation of taste signaling pathways. These methods of screening can be used to identify high affinity agonists and antagonists of taste cell activity. These modulatory compounds can then be used in the food and pharmaceutical industries to customize taste, e.g., to modulate the sweet tastes of foods or drugs.

[0040] Thus, the invention provides assays for detecting and characterizing taste modulation, wherein T1R family members act as direct or indirect reporter molecules of the effect of modulators on taste transduction. GPCRs can be used in assays to, e.g., measure changes in ligand binding, ion concentration, membrane potential, current flow, ion flux, transcription, signal transduction, receptor-ligand interactions, second messenger concentrations, in vitro, in vivo, and ex vivo. In one embodiment, members of the T1R family can be used as indirect reporters via attachment to a second reporter molecule such as green fluorescent protein (see, e.g., Mistili & Spector, Nature Biotechnology, 15:961-964 (1997)). In another embodiment, T1R family members may be recombinantly expressed in cells, and modulation of taste transduction via GPCR activity may be assayed by measuring changes in Ca²⁺ levels and other intracellular messages such as cAMP, cGMP, or IP3.

[0041] In certain embodiments, a domain of a T1R polypeptide, e.g., an extracellular, transmembrane, or intracellular domain, is fused to a heterologous polypeptide, thereby forming a chimeric polypeptide, e.g., a chimeric polypeptide with GPCR activity. Such chimeric polypeptides are useful, e.g., in assays to identify ligands, agonists, antagonists, or other modulators of a T1R polypeptide. In addition, such chimeric polypeptides are useful to create novel taste receptors with novel ligand binding specificity, modes of regulation, signal transduction pathways, or other such properties, or to create novel taste receptors with novel combinations of ligand binding specificity, modes of regulation, signal transduction pathways, etc.

[0042] In one embodiment, a T1R polypeptide is expressed in a eukaryotic cell as a chimeric receptor with a heterologous, chaperone sequence that facilitates plasma membrane trafficking, or maturation and targeting through the secretory pathway. The optional heterologous sequence may be a rhodopsin sequence, such as an N-terminal fragment of a rhodopsin. Such chimeric T1R receptors can be expressed in any eukaryotic cell, such as HEK-293 cells. Preferably, the cells comprise a G protein, e.g., Gα15 or Gα16 or another type of promiscuous G protein capable of pairing a wide range of chemosensory GPCRs to an intracellular signaling pathway or to a signaling protein such as phospholipase C. Alternatively, the cells may express a chimeric or variant G protein that is selected based on its ability to couple with T1Rs to produce a functional T1R taste receptor. Examples of variant G proteins which are especially preferred include the G protein variants disclosed in U.S. Ser. No. 09/984,292, filed on Oct. 29, 2001, incorporated by reference herein in its entirety and the chimeric Gal 5 variants disclosed in U.S. Provisional Application No. ______, Attorney Docket No. 078003-0280737 also incorporated by reference in its entirety. These applications disclose G protein variants that have been shown to couple better with T1Rs than Gα15, a well known promiscuous G protein. Activation of such chimeric receptors in such cells can be detected using any standard method, such as by detecting changes in intracellular calcium by detecting FURA-2 dependent fluorescence in the cell. If preferred host cells do not express an appropriate G protein, they may be transfected with a gene encoding a promiscuous G protein such as those described in U.S. Application Serial No. 60/243,770, which is herein incorporated by reference in its entirety.

[0043] Methods of assaying for modulators of taste transduction include in vitro ligand-binding assays using: T1R polypeptides, portions thereof, i.e., the extracellular domain, transmembrane region, or combinations thereof, or chimeric proteins comprising one or more domains of a T1R family member; oocyte or tissue culture cells expressing T1R polypeptides, fragments, or fusion proteins; phosphorylation and dephosphorylation of T1R family members; G protein binding to GPCRs; ligand-binding assays; voltage, membrane potential and conductance changes; ion flux assays; changes in intracellular second messengers such as cGMP, CAMP and inositol triphosphate; changes in intracellular calcium levels; and neurotransmitter release.

[0044] Further, the invention provides methods of detecting T1R nucleic acid and protein expression, allowing investigation of taste transduction regulation and specific identification of taste receptor cells. T1R family members also provide useful nucleic acid probes for paternity and forensic investigations. T1R genes are also useful as a nucleic acid probes for identifying taste receptor cells, such as foliate, fungiform, circumvallate, geschmackstreifen, and epiglottis taste receptor cells. T1R receptors can also be used to generate monoclonal and polyclonal antibodies useful for identifying taste receptor cells. Taste receptor cells can be identified using techniques such as reverse transcription and amplification of mRNA, isolation of total RNA or poly A+ RNA, northern blotting, dot blotting, in situ hybridization, RNase protection, S1 digestion, probing DNA microchip arrays, western blots, and the like.

[0045] Functionally, the T1R polypeptides comprise a family of related seven transmembrane G protein-coupled receptors, which are believed to be involved in taste transduction and may interact with a G protein to mediate taste signal transduction (see, e.g., Fong, Cell Signal, 8:217 (1996); Baldwin, Curr. Opin. Cell Biol., 6:180 (1994)). Structurally, the nucleotide sequences of T1R family members may encode related polypeptides comprising an extracellular domain, seven transmembrane domains, and a cytoplasmic domain. Related T1R family genes from other species share at least about 50%, and optionally 60%, 70%, 80%, or 90%, nucleotide sequence identity over a region of at least about 50 nucleotides in length, optionally 100, 200, 500, or more nucleotides in length to SEQ ID NOS: 1, 2, 3, 9, 11, 13, 15, 16, 20, or conservatively modified variants thereof, or encode polypeptides sharing at least about 35 to 50%, and optionally 60%, 70%, 80%, or 90%, amino acid sequence identity over an amino acid region at least about 25 amino acids in length, optionally 50 to 100 amino acids in length to SEQ ID NOS: 4, 10, 12, 14, 17, 21, or conservatively modified variants thereof.

[0046] Several consensus amino acid sequences or domains have also been identified that are characteristic of T1R family members. For example, T1R family members typically comprise a sequence having at least about 50%, optionally 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95-99%, or higher, identity to T1R consensus sequences 1 and 2 (SEQ ID NOs 18 and 19, respectively). These conserved domains thus can be used to identify members of the T1R family, by identity, specific hybridization or amplification, or specific binding by antibodies raised against a domain. Such T1R consensus sequences have the following amino acid sequences: T1R Family Consensus Sequence 1: (SEQ ID NO: 18) (TR)C(FL)(RQP)R(RT)(SPV)(VERKT)FL(AE)(WL)(RHG)E T1R Family Consensus Sequence 2: (SEQ ID NO: 19) (LQ)P(EGT)(NRC)YN(RE)A(RK)(CGF)(VLI)T(FL)(AS)(ML)

[0047] These consensus sequences are inclusive of those found in the T1R polypeptides described herein, but T1R family members from other organisms may be expected to comprise consensus sequences having about 75% identity or more to the inclusive consensus sequences described specifically herein.

[0048] Specific regions of the T1R nucleotide and amino acid sequences may be used to identify polymorphic variants, interspecies homologs, and alleles of T1R family members. This identification can be made in vitro, e.g., under stringent hybridization conditions or PCR (e.g., using primers encoding the T1R consensus sequences identified above), or by using the sequence information in a computer system for comparison with other nucleotide sequences. Different alleles of T1R genes within a single species population will also be useful in determining whether differences in allelic sequences correlate to differences in taste perception between members of the population. Classical PCR-type amplification and cloning techniques are useful for isolating orthologs, for example, where degenerate primers are sufficient for detecting related genes across species, which typically have a higher level of relative identity than paralogous members of the T1R family within a single species.

[0049] For instance, degenerate primers SAP077 (SEQ. ID NO. 5) and SAP0079 (SEQ. ID NO. 6) can be used can be used to amplify and clone T1R3 genes from different mammalian genomes. In contrast, genes within a single species that are related to T1R3 are best identified using sequence pattern recognition software to look for related sequences. Typically, identification of polymorphic variants and alleles of T1R family members can be made by comparing an amino acid sequence of about 25 amino acids or more, e.g., 50-100 amino acids. Amino acid identity of approximately at least 35 to 50%, and optionally 60%, 70%, 75%, 80%, 85%, 90%, 95-99%, or above typically demonstrates that a protein is a polymorphic variant, interspecies homolog, or allele of a T1R family member. Sequence comparison can be performed using any of the sequence comparison algorithms discussed below. Antibodies that bind specifically to T1R polypeptides or a conserved region thereof can also be used to identify alleles, interspecies homologs, and polymorphic variants.

[0050] Polymorphic variants, interspecies homologs, and alleles of T1R genes can be confirmed by examining taste-cell-specific expression of the putative T1R polypeptide. Typically, T1R polypeptides having an amino acid sequence disclosed herein can be used as a positive control in comparison to the putative T1R polypeptide to demonstrate the identification of a polymorphic variant or allele of the T1R family member. The polymorphic variants, alleles, and interspecies homologs are expected to retain the seven transmembrane structure of a G protein-coupled receptor. For further detail, see WO 00/06592, which discloses related T1R family members, GPCR-B3s, the contents of which are herein incorporated by reference in a manner consistent with this disclosure. GPCR-B3 receptors are referred to herein as rT1R1 and mT1R1. Additionally, see WO 00/06593, which also discloses related T1R family members, GPCR-B4s, the contents of which are herein incorporated by reference in a manner consistent with this disclosure. GPCR-B4 receptors are referred to herein as rT1R2 and mT1R2.

[0051] Nucleotide and amino acid sequence information for T1R family members may also be used to construct models of taste-cell-specific polypeptides in a computer system. These models can be subsequently used to identify compounds that can activate or inhibit T1R receptor proteins. Such compounds that modulate the activity of T1R family members can then be used to investigate the role of T1R genes and receptors in taste transduction.

[0052] The present invention also provides assays, preferably high throughput assays, to identify molecules that interact with and/or modulate a T1R polypeptide. In numerous assays, a particular domain of a T1R family member is used, e.g., an extracellular, transmembrane, or intracellular domain or region. In numerous embodiments, an extracellular domain, transmembrane region or combination thereof may be bound to a solid substrate, and used, e.g., to isolate ligands, agonists, antagonists, or any other molecules that can bind to and/or modulate the activity of a T1R polypeptide.

[0053] In one aspect of the invention, a new human GPCR gene of the T1R family, termed hTIR3, is provided. The hT1R3 gene was identified from the human genome sequence database including the HTGS division of GenBank. The nucleotide and conceptually translated amino acid sequence for hT1R3 are provided in SEQ. ID NOS 1-4. The hT1R3 receptor was identified in the partially sequenced BAC genomic clone RP5-89003 (database accession number AL139287) by virtue of its sequence similarity to the candidate rat taste receptor rT1R1 (accession number AF127389). By reference, the pairwise identity between the predicted hT1R3 and rT1R1 protein sequences is approximately 34%. Sequence comparisons with additional members of the GPCR Family C (which includes the calcium-sensing receptors, putative V2R pheromone receptors, GABA-B receptors, fish taste receptors, and metabotropic glutamate receptors) indicate that hT1R3 is likely to belong to the Family C subgroup defined by T1R1 and a second rat candidate taste receptor (rT1R2, accession number AF127390).

[0054] The invention also provides the human ortholog, termed hT1R1, of a rat taste receptor, designated rT1R1. The gene products of rT1R1 and hT1R1 are approximately 74% identical. The mouse gene, mT1R1 has been reported, see Hoon et al., Cell, 96:541-551 (2000), and maps to a chromosomal interval homologous to the interval containing hT1R1. The nucleotide and conceptually-translated hT1R1 sequences are described herein as SEQ. ID NOS 15 and 16, respectively.

[0055] While not wishing to be bound to any particular theory, the T1R family of receptors is predicted to be involved in sweet taste transduction by virtue of the linkage of mTIR3 to the Sac locus, a locus on the distal end of chromosome four that influences sweet taste. Human T1R3 has also been reported to localize to 1p36.2-1p36.33, a region that displays conserved synteny with the mouse interval containing Sac and T1R1. However, T1R type receptors may mediate other taste modalities, such as bitter, umami, sour and salty.

[0056] Various conservative mutations and substitutions are envisioned to be within the scope of the invention. For instance, it would be within the level of skill in the art to perform amino acid substitutions using known protocols of recombinant gene technology including PCR, gene cloning, site-directed mutagenesis of cDNA, transfection of host cells, and in-vitro transcription. The variants could then be screened for taste-cell-specific GPCR functional activity.

[0057] A. Identification and Characterization of T1R Polypeptides

[0058] The amino acid sequences of the T1R proteins and polypeptides of the invention can be identified by putative translation of the coding nucleic acid sequences. These various amino acid sequences and the coding nucleic acid sequences may be compared to one another or to other sequences according to a number of methods.

[0059] For example, in sequence comparison, typically one sequence acts as a reference sequence, to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are entered into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. Default program parameters can be used, as described below for the BLASTN and BLASTP programs, or alternative parameters can be designated. The sequence comparison algorithm then calculates the percent sequence identities for the test sequences relative to the reference sequence, based on the program parameters.

[0060] A “comparison window,” as used herein, includes reference to a segment of any one of the number of contiguous positions selected from the group consisting of from 20 to 600, usually about 50 to about 200, more usually about 100 to about 150 in which a sequence may be compared to a reference sequence of the same number of contiguous positions after the two sequences are optimally aligned. Methods of alignment of sequences for comparison are well known in the art. Optimal alignment of sequences for comparison can be conducted, e.g., by the local homology algorithm of Smith & Waterman, Adv. Appl. Math. 2:482 (1981), by the homology alignment algorithm of Needleman & Wunsch, J. Mol. Biol. 48:443 (1970), by the search for similarity method of Pearson & Lipman, Proc. Nat. Acad. Sci. USA 85:2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by manual alignment and visual inspection (see, e.g., Current Protocols in Molecular Biology (Ausubel et al., eds. 1995 supplement)).

[0061] A preferred example of an algorithm that is suitable for determining percent sequence identity and sequence similarity are the BLAST and BLAST 2.0 algorithms, which are described in Altschul et al., Nuc. Acids Res. 25:3389-3402 (1977) and Altschul et al., J. Mol. Biol. 215:403-410 (1990), respectively. Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/). This algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length W in the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul et al., Altschul et al., Nuc. Acids Res. 25:3389-3402 (1977) and Altschul et al., J. Mol. Biol. 215:403410 (1990)). These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always >0) and N (penalty score for mismatching residues; always <0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. The BLAST algorithm parameters W, T, and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a wordlength (W) of 11, an expectation (E) or 10, M=5, N=−4 and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults a wordlength of 3, and expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff & Henikoff, Proc. Natl. Acad. Sci. USA 89:10915 (1989)) alignments (B) of 50, expectation (E) of 10, M=5, N=4, and a comparison of both strands.

[0062] Another example of a useful algorithm is PILEUP. PILEUP creates a multiple sequence alignment from a group of related sequences using progressive, pairwise alignments to show relationship and percent sequence identity. It also plots a so-called “tree” or “dendogram” showing the clustering relationships used to create the alignment (see, e.g., FIG. 2). PILEUP uses a simplification of the progressive alignment method of Feng & Doolittle, J. Mol. Evol. 35:351-360 (1987). The method used is similar to the method described by Higgins & Sharp, CABIOS 5:151-153 (1989). The program can align up to 300 sequences, each of a maximum length of 5,000 nucleotides or amino acids. The multiple alignment procedure begins with the pairwise alignment of the two most similar sequences, producing a cluster of two aligned sequences. This cluster is then aligned to the next most related sequence or cluster of aligned sequences. Two clusters of sequences are aligned by a simple extension of the pairwise alignment of two individual sequences. The final alignment is achieved by a series of progressive, pairwise alignments. The program is run by designating specific sequences and their amino acid or nucleotide coordinates for regions of sequence comparison and by designating the program parameters. Using PILEUP, a reference sequence is compared to other test sequences to determine the percent sequence identity relationship using the following parameters: default gap weight (3.00), default gap length weight (0.10), and weighted end gaps. PILEUP can be obtained from the GCG sequence analysis software package, e.g., version 7.0 (Devereaux et al., Nuc. Acids Res. 12:387-395 (1984) encoded by the genes were derived by conceptual translation of the corresponding open reading frames. Comparison of these protein sequences to all known proteins in the public sequence databases using BLASTP algorithm revealed their strong homology to the members of the T1R family, each of the T1R family sequences having at least about 35 to 50%, and preferably at least 55%, at least 60%, at least 65%, and most preferably at least 70%, amino acid identity to at least one known member of the family.

[0063] B. Definitions

[0064] As used herein, the following terms have the meanings ascribed to them unless specified otherwise.

[0065] “Taste cells” include neuroepithelial cells that are organized into groups to form taste buds of the tongue, e.g., foliate, fungiform, and circumvallate cells (see, e.g., Roper et al., Ann. Rev. Neurosci. 12:329-353 (1989)). Taste cells are also found in the palate and other tissues, such as the esophagus and the stomach.

[0066] “T1R” refers to one or more members of a family of G protein-coupled receptors that are expressed in taste cells such as foliate, fungiform, and circumvallate cells, as well as cells of the palate, and esophagus (see, e.g., Hoon et al., Cell, 96:541-551 (1999), herein incorporated by reference in its entirety). Members of this family are also referred to as GPCR-B3 and TR1 in WO 00/06592 as well as GPCR-B4 and TR2 in WO 00/06593. GPCR-B3 is also herein referred to as rT1R1, and GPCR-B4 is referred to as rT1R2. Taste receptor cells can also be identified on the basis of morphology (see, e.g., Roper, supra), or by the expression of proteins specifically expressed in taste cells. T1R family members may have the ability to act as receptors for sweet taste transduction, or to distinguish between various other taste modalities.

[0067] “T1R” nucleic acids encode a family of GPCRs with seven transmembrane regions that have “G protein-coupled receptor activity,” e.g., they may bind to G proteins in response to extracellular stimuli and promote production of second messengers such as IP3, cAMP, cGMP, and Ca²⁺ via stimulation of enzymes such as phospholipase C and adenylate cyclase (for a description of the structure and function of GPCRs, see, e.g., Fong, supra, and Baldwin, supra). A single taste cell may contain many distinct T1R polypeptides.

[0068] The term “T1R” family therefore refers to polymorphic variants, alleles, mutants, and interspecies homologs that: (1) have at least about 35 to 50% amino acid sequence identity, optionally about 60, 75, 80, 85, 90, 95, 96, 97, 98, or 99% amino acid sequence identity to SEQ ID NOS: 4, 10, 12, 14, 17, or 21 over a window of about 25 amino acids, optionally 50-100 amino acids; (2) specifically bind to antibodies raised against an immunogen comprising an amino acid sequence selected from the group consisting of SEQ ID NOS: 4, 10, 12, 14, 17, 21 and conservatively modified variants thereof; (3) are encoded by a nucleic acid molecule which specifically hybridize (with a size of at least about 100, optionally at least about 500-1000 nucleotides) under stringent hybridization conditions to a sequence selected from the group consisting of SEQ ID NOS: 1, 2, 3, 9, 11, 13, 15, 16, 20, and conservatively modified variants thereof; (4) comprise a sequence at least about 35 to 50% identical to an amino acid sequence selected from the group consisting of SEQ ID NOS: 4, 10, 12, 14, 17, or 21; or (5) are amplified by primers that specifically hybridize under stringent hybridization conditions to the same sequence as degenerate primer sets encoding SEQ ID NOS: 7, 8, and conservatively modified variants thereof.

[0069] Topologically, certain chemosensory GPCRs have an “N-terminal domain;” “extracellular domains;” “transmembrane domains” comprising seven transmembrane regions, and corresponding cytoplasmic, and extracellular loops; “cytoplasmic domains,” and a “C-terminal domain” (see, e.g., Hoon et al., Cell, 96:541-551 (1999); Buck & Axel, Cell, 65:175-187 (1991)). These domains can be structurally identified using methods known to those of skill in the art, such as sequence analysis programs that identify hydrophobic and hydrophilic domains (see, e.g., Stryer, Biochemistry, (3rd ed. 1988); see also any of a number of Internet based sequence analysis programs, such as those found at dot.imgen.bcm.tmc.edu). Such domains are useful for making chimeric proteins and for in vitro assays of the invention, e.g., ligand-binding assays.

[0070] “Extracellular domains” therefore refers to the domains of T1R polypeptides that protrude from the cellular membrane and are exposed to the extracellular face of the cell. Such domains generally include the “N terminal domain” that is exposed to the extracellular face of the cell, and optionally can include portions of the extracellular loops of the transmembrane domain that are exposed to the extracellular face of the cell, i.e., the loops between transmembrane regions 2 and 3, between transmembrane regions 4 and 5, and between transmembrane regions 6 and 7.

[0071] The “N terminal domain” region starts at the N-terminus and extends to a region close to the start of the transmembrane domain. More particularly, in one embodiment of the invention, this domain starts at the N-terminus and ends approximately at the conserved glutamic acid at amino acid position 563 plus or minus approximately 20 amino acid. These extracellular domains are useful for in vitro ligand-binding assays, both soluble and solid phase. In addition, transmembrane regions, described below, can also bind ligand either in combination with the extracellular domain, and are therefore also useful for in vitro ligand-binding assays.

[0072] “Transmembrane domain,” which comprises the seven “transmembrane regions,” refers to the domain of T1R polypeptides that lies within the plasma membrane, and may also include the corresponding cytoplasmic (intracellular) and extracellular loops. In one embodiment, this region corresponds to the domain of T1R family members which starts approximately at the conserved glutamic acid residue at amino acid position 563 plus or minus 20 amino acids and ends approximately at the conserved tyrosine amino acid residue at position 812 plus or minus approximately 10 amino acids. The seven transmembrane regions and extracellular and cytoplasmic loops can be identified using standard methods, as described in Kyte & Doolittle, J. Mol. Biol., 157:105-32 (1982)), or in Stryer, supra.

[0073] “Cytoplasmic domains” refers to the domains of T1R polypeptides that face the inside of the cell, e.g., the “C terminal domain” and the intracellular loops of the transmembrane domain, e.g., the intracellular loop between transmembrane regions 1 and 2, the intracellular loop between transmembrane regions 3 and 4, and the intracellular loop between transmembrane regions 5 and 6. “C terminal domain” refers to the region that spans the end of the last transmembrane domain and the C-terminus of the protein, and which is normally located within the cytoplasm. In one embodiment, this region starts at the conserved tyrosine amino acid residue at position 812 plus or minus approximately 10 amino acids and continues to the C-terminus of the polypeptide.

[0074] The term “ligand-binding region” or “ligand-binding domain” refers to sequences derived from a chemosensory receptor, particularly a taste receptor, that substantially incorporates at least the extracellular domain of the receptor. In one embodiment, the extracellular domain of the ligand-binding region may include the N-terminal domain and, optionally, portions of the transmembrane domain, such as the extracellular loops of the transmembrane domain. The ligand-binding region may be capable of binding a ligand, and more particularly, a taste stimulus.

[0075] The phrase “functional effects” in the context of assays for testing compounds that modulate T1R family member mediated taste transduction includes the determination of any parameter that is indirectly or directly under the influence of the receptor, e.g., functional, physical and chemical effects. It includes ligand binding, changes in ion flux, membrane potential, current flow, transcription, G protein binding, GPCR phosphorylation or dephosphorylation, signal transduction, receptor-ligand interactions, second messenger concentrations (e.g., cAMP, cGMP, IP3, or intracellular Ca²⁺), in vitro, in vivo, and ex vivo and also includes other physiologic effects such increases or decreases of neurotransmitter or hormone release.

[0076] By “determining the functional effect” in the context of assays is meant assays for a compound that increases or decreases a parameter that is indirectly or directly under the influence of a T1R family member, e.g., functional, physical and chemical effects. Such functional effects can be measured by any means known to those skilled in the art, e.g., changes in spectroscopic characteristics (e.g., fluorescence, absorbance, refractive index), hydrodynamic (e.g., shape), chromatographic, or solubility properties, patch clamping, voltage-sensitive dyes, whole cell currents, radioisotope efflux, inducible markers, oocyte T1R gene expression; tissue culture cell T1R expression; transcriptional activation of T1R genes; ligand-binding assays; voltage, membrane potential and conductance changes; ion flux assays; changes in intracellular second messengers such as cAMP, cGMP, and inositol triphosphate (IP3); changes in intracellular calcium levels; neurotransmitter release, and the like.

[0077] “Inhibitors,” “activators,” and “modulators” of T1R genes or proteins are used interchangeably to refer to inhibitory, activating, or modulating molecules identified using in vitro and in vivo assays for taste transduction, e.g., ligands, agonists, antagonists, and their homologs and mimetics. Inhibitors are compounds that, e.g., bind to, partially or totally block stimulation, decrease, prevent, delay activation, inactivate, desensitize, or down regulate taste transduction, e.g., antagonists. Activators are compounds that, e.g., bind to, stimulate, increase, open, activate, facilitate, enhance activation, sensitize, or up regulate taste transduction, e.g., agonists. Modulators include compounds that, e.g., alter the interaction of a receptor with: extracellular proteins that bind activators or inhibitor (e.g., ebnerin and other members of the hydrophobic carrier family); G proteins; kinases (e.g., homologs of rhodopsin kinase and beta adrenergic receptor kinases that are involved in deactivation and desensitization of a receptor); and arrestins, which also deactivate and desensitize receptors. Modulators can include genetically modified versions of T1R family members, e.g., with altered activity, as well as naturally occurring and synthetic ligands, antagonists, agonists, small chemical molecules and the like. Such assays for inhibitors and activators include, e.g., expressing T1R family members in cells or cell membranes, applying putative modulator compounds, in the presence or absence of taste stimuli, e.g., sweet taste stimuli, and then determining the functional effects on taste transduction, as described above. Samples or assays comprising T1R family members that are treated with a potential activator, inhibitor, or modulator are compared to control samples without the inhibitor, activator, or modulator to examine the extent of modulation. Control samples (untreated with modulators) are assigned a relative T1R activity value of 100%. Inhibition of a T1R is achieved when the T1R activity value relative to the control is about 80%, optionally 50% or 25-0%. Activation of a T1R is achieved when the T1R activity value relative to the control is 110%, optionally 150%, optionally 200-500%, or 1000-3000% higher.

[0078] The terms “purified,” “substantially purified,” and “isolated” as used herein refer to the state of being free of other, dissimilar compounds with which the compound of the invention is normally associated in its natural state, so that the “purified,” “substantially purified,” and “isolated” subject comprises at least 0.5%, 1%, 5%, 10%, or 20%, and most preferably at least 50% or 75% of the mass, by weight, of a given sample. In one preferred embodiment, these terms refer to the compound of the invention comprising at least 95% of the mass, by weight, of a given sample. As used herein, the terms “purified,” “substantially purified,” and “isolated” “isolated,” when referring to a nucleic acid or protein, of nucleic acids or proteins, also refers to a state of purification or concentration different than that which occurs naturally in the mammalian, especially human, body. Any degree of purification or concentration greater than that which occurs naturally in the mammalian, especially human, body, including (1) the purification from other associated structures or compounds or (2) the association with structures or compounds to which it is not normally associated in the mammalian, especially human, body, are within the meaning of “isolated.” The nucleic acid or protein or classes of nucleic acids or proteins, described herein, may be isolated, or otherwise associated with structures or compounds to which they are not normally associated in nature, according to a variety of methods and processes known to those of skill in the art.

[0079] As used herein, the term “isolated,” when referring to a nucleic acid or polypeptide refers to a state of purification or concentration different than that which occurs naturally in the mammalian, especially human, body. Any degree of purification or concentration greater than that which occurs naturally in the body, including (1) the purification from other naturally-occurring associated structures or compounds, or (2) the association with structures or compounds to which it is not normally associated in the body are within the meaning of “isolated” as used herein. The nucleic acids or polypeptides described herein may be isolated or otherwise associated with structures or compounds to which they are not normally associated in nature, according to a variety of methods and processed known to those of skill in the art.

[0080] As used herein, the terms “amplifying” and “amplification” refer to the use of any suitable amplification methodology for generating or detecting recombinant or naturally expressed nucleic acid, as described in detail, below. For example, the invention provides methods and reagents (e.g., specific degenerate oligonucleotide primer pairs) for amplifying (e.g., by polymerase chain reaction, PCR) naturally expressed (e.g., genomic or mRNA) or recombinant (e.g., cDNA) nucleic acids of the invention (e.g., taste stimulus-binding sequences of the invention) in vivo or in vitro.

[0081] The term “7-transmembrane receptor” means a polypeptide belonging to a superfamily of transmembrane proteins that have seven domains that span the plasma membrane seven times (thus, the seven domains are called “transmembrane” or “TM” domains TM I to TM VII). The families of olfactory and certain taste receptors each belong to this super-family. 7-transmembrane receptor polypeptides have similar and characteristic primary, secondary and tertiary structures, as discussed in further detail below.

[0082] The term “library” means a preparation that is a mixture of different nucleic acid or polypeptide molecules, such as the library of recombinantly generated chemosensory, particularly taste receptor ligand-binding domains generated by amplification of nucleic acid with degenerate primer pairs, or an isolated collection of vectors that incorporate the amplified ligand-binding domains, or a mixture of cells each randomly transfected with at least one vector encoding an taste receptor.

[0083] The term “nucleic acid” or “nucleic acid sequence” refers to a deoxy-ribonucleotide or ribonucleotide oligonucleotide in either single- or double-stranded form. The term encompasses nucleic acids, i.e., oligonucleotides, containing known analogs of natural nucleotides. The term also encompasses nucleic-acid-like structures with synthetic backbones (see e.g., Oligonucleotides and Analogues, a Practical Approach, ed. F. Eckstein, Oxford Univ. Press (1991); Antisense Strategies, Annals of the N.Y. Academy of Sciences, Vol. 600, Eds. Baserga et al. (NYAS 1992); Milligan J. Med. Chem. 36:1923-1937 (1993); Antisense Research and Applications (1993, CRC Press), WO 97/03211; WO 96/39154; Mata, Toxicol. Appl. Pharmacol. 144:189-197 (1997); Strauss-Soukup, Biochemistry 36:8692-8698 (1997); Samstag, Antisense Nucleic Acid Drug Dev, 6:153-156 (1996)).

[0084] Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions) and complementary sequences, as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating, e.g., sequences in which the third position of one or more selected codons is substituted with mixed-base and/or deoxyinosine residues (Batzer et al., Nucleic Acid Res., 19:5081 (1991); Ohtsuka et al., J. Biol. Chem., 260:2605-2608 (1985); Rossolini et al., Mol. Cell. Probes, 8:91-98 (1994)). The term nucleic acid is used interchangeably with gene, cDNA, mRNA, oligonucleotide, and polynucleotide.

[0085] The terms “polypeptide,” “peptide” and “protein” are used interchangeably herein to refer to a polymer of amino acid residues. The terms apply to amino acid polymers in which one or more amino acid residue is an artificial chemical mimetic of a corresponding naturally occurring amino acid, as well as to naturally occurring amino acid polymers and non-naturally occurring amino acid polymer.

[0086] The term “plasma membrane translocation domain” or simply “translocation domain” means a polypeptide domain that, when incorporated into the amino terminus of a polypeptide coding sequence, can with great efficiency “chaperone” or “translocate” the hybrid (“fusion”) protein to the cell plasma membrane. For instance, a “translocation domain” may be derived from the amino terminus of the bovine rhodopsin receptor polypeptide, a 7-transmembrane receptor. However, rhodopsin from any mammal may be used, as can other translocation facilitating sequences. Thus, the translocation domain is particularly efficient in translocating 7-transmembrane fusion proteins to the plasma membrane, and a protein (e.g., a taste receptor polypeptide) comprising an amino terminal translocating domain will be transported to the plasma membrane more efficiently than without the domain. However, if the N-terminal domain of the polypeptide is active in binding, the use of other translocation domains may be preferred.

[0087] The “translocation domain,” “ligand-binding domain”, and chimeric receptors compositions described herein also include “analogs,” or “conservative variants” and “mimetics” (“peptidomimetics”) with structures and activity that substantially correspond to the exemplary sequences. Thus, the terms “conservative variant” or “analog” or “mimetic” refer to a polypeptide which has a modified amino acid sequence, such that the change(s) do not substantially alter the polypeptide's (the conservative variant's) structure and/or activity, as defined herein. These include conservatively modified variations of an amino acid sequence, i.e., amino acid substitutions, additions or deletions of those residues that are not critical for protein activity, or substitution of amino acids with residues having similar properties (e.g., acidic, basic, positively or negatively charged, polar or non-polar, etc.) such that the substitutions of even critical amino acids does not substantially alter structure and/or activity.

[0088] More particularly, “conservatively modified variants” applies to both amino acid and nucleic acid sequences. With respect to particular nucleic acid sequences, conservatively modified variants refers to those nucleic acids which encode identical or essentially identical amino acid sequences, or where the nucleic acid does not encode an amino acid sequence, to essentially identical sequences. Because of the degeneracy of the genetic code, a large number of functionally identical nucleic acids encode any given protein.

[0089] For instance, the codons GCA, GCC, GCG and GCU all encode the amino acid alanine. Thus, at every position where an alanine is specified by a codon, the codon can be altered to any of the corresponding codons described without altering the encoded polypeptide.

[0090] Such nucleic acid variations are “silent variations,” which are one species of conservatively modified variations. Every nucleic acid sequence herein which encodes a polypeptide also describes every possible silent variation of the nucleic acid. One of skill will recognize that each codon in a nucleic acid (except AUG, which is ordinarily the only codon for methionine, and TGG, which is ordinarily the only codon for tryptophan) can be modified to yield a functionally identical molecule. Accordingly, each silent variation of a nucleic acid which encodes a polypeptide is implicit in each described sequence.

[0091] Conservative substitution tables providing functionally similar amino acids are well known in the art. For example, one exemplary guideline to select conservative substitutions includes (original residue followed by exemplary substitution): ala/gly or ser; arg/lys; asn/gln or his; asp/glu; cys/ser; gln/asn; gly/asp; gly/ala or pro; his/asn or gin; ile/leu or val; leu/ile or val; lys/arg or gin or glu; met/leu or tyr or ile; phe/met or leu or tyr; ser/thr; thr/ser; trp/tyr; tyr/trp or phe; val/ile or leu. An alternative exemplary guideline uses the following six groups, each containing amino acids that are conservative substitutions for one another: 1) Alanine (A), Serine (S), Threonine (T); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q); 4) Arginine (R), Lysine (1); 5) Isoleucine (1), Leucine (L), Methionine (M), Valine (V); and 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W); (see also, e.g., Creighton, Proteins, W. H. Freeman and Company (1984); Schultz and Schimer, Principles of Protein Structure, Springer-Vrlag (1979)). One of skill in the art will appreciate that the above-identified substitutions are not the only possible conservative substitutions. For example, for some purposes, one may regard all charged amino acids as conservative substitutions for each other whether they are positive or negative. In addition, individual substitutions, deletions or additions that alter, add or delete a single amino acid or a small percentage of amino acids in an encoded sequence can also be considered “conservatively modified variations.”

[0092] The terms “mimetic” and “peptidomimetic” refer to a synthetic chemical compound that has substantially the same structural and/or functional characteristics of the polypeptides, e.g., translocation domains, ligand-binding domains, or chimeric receptors of the invention. The mimetic can be either entirely composed of synthetic, non-natural analogs of amino acids, or may be a chimeric molecule of partly natural peptide amino acids and partly non-natural analogs of amino acids. The mimetic can also incorporate any amount of natural amino acid conservative substitutions as long as such substitutions also do not substantially alter the mimetic's structure and/or activity.

[0093] As with polypeptides of the invention which are conservative variants, routine experimentation will determine whether a mimetic is within the scope of the invention, i.e., that its structure and/or function is not substantially altered. Polypeptide mimetic compositions can contain any combination of non-natural structural components, which are typically from three structural groups: a) residue linkage groups other than the natural amide bond (“peptide bond”) linkages; b) non-natural residues in place of naturally occurring amino acid residues; or c) residues which induce secondary structural mimicry, i.e., to induce or stabilize a secondary structure, e.g., a beta turn, gamma turn, beta sheet, alpha helix conformation, and the like. A polypeptide can be characterized as a mimetic when all or some of its residues are joined by chemical means other than natural peptide bonds. Individual peptidomimetic residues can be joined by peptide bonds, other chemical bonds or coupling means, such as, e.g., glutaraldehyde, N-hydroxysuccinimide esters, bifunctional maleimides, N,N′-dicyclohexylcarbodiimide (DCC) or N,N′-diisopropylcarbodiimide (DIC). Linking groups that can be an alternative to the traditional amide bond (“peptide bond”) linkages include, e.g., ketomethylene (e.g., —C(═O)—CH₂— for —C(═O)—NH—), aminomethylene (CH₂—NH), ethylene, olefin (CH═CH), ether (CH₂—O), thioether (CH₂—S), tetrazole (CN₄), thiazole, retroamide, thioamide, or ester (see, e.g., Spatola, Chemistry and Biochemistry of Amino Acids, Peptides and Proteins, Vol. 7, pp 267-357, “Peptide Backbone Modifications,” Marcell Dekker, NY (1983)). A polypeptide can also be characterized as a mimetic by containing all or some non-natural residues in place of naturally occurring amino acid residues; non-natural residues are well described in the scientific and patent literature.

[0094] A “label” or a “detectable moiety” is a composition detectable by spectroscopic, photochemical, biochemical, immunochemical, or chemical means. For example, useful labels include ³²P, fluorescent dyes, electron-dense reagents, enzymes (e.g., as commonly used in an ELISA), biotin, digoxigenin, or haptens and proteins which can be made detectable, e.g., by incorporating a radiolabel into the peptide or used to detect antibodies specifically reactive with the peptide.

[0095] A “labeled nucleic acid probe or oligonucleotide” is one that is bound, either covalently, through a linker or a chemical bond, or noncovalently, through ionic, van der Waals, electrostatic, or hydrogen bonds to a label such that the presence of the probe may be detected by detecting the presence of the label bound to the probe.

[0096] As used herein a “nucleic acid probe or oligonucleotide” is defined as a nucleic acid capable of binding to a target nucleic acid of complementary sequence through one or more types of chemical bonds, usually through complementary base pairing, usually through hydrogen bond formation. As used herein, a probe may include natural (i.e., A, G, C, or T) or modified bases (7-deazaguanosine, inosine, etc.). In addition, the bases in a probe may be joined by a linkage other than a phosphodiester bond, so long as it does not interfere with hybridization. Thus, for example, probes may be peptide nucleic acids in which the constituent bases are joined by peptide bonds rather than phosphodiester linkages. It will be understood by one of skill in the art that probes may bind target sequences lacking complete complementarity with the probe sequence depending upon the stringency of the hybridization conditions. The probes are optionally directly labeled as with isotopes, chromophores, lumiphores, chromogens, or indirectly labeled such as with biotin to which a streptavidin complex may later bind. By assaying for the presence or absence of the probe, one can detect the presence or absence of the select sequence or subsequence.

[0097] The term “heterologous” when used with reference to portions of a nucleic acid indicates that the nucleic acid comprises two or more subsequences that are not found in the same relationship to each other in nature. For instance, the nucleic acid is typically recombinantly produced, having two or more sequences from unrelated genes arranged to make a new functional nucleic acid, e.g., a promoter from one source and a coding region from another source. Similarly, a heterologous protein indicates that the protein comprises two or more subsequences that are not found in the same relationship to each other in nature (e.g., a fusion protein).

[0098] A “promoter” is defined as an array of nucleic acid sequences that direct transcription of a nucleic acid. As used herein, a promoter includes necessary nucleic acid sequences near the start site of transcription, such as, in the case of a polymerase 11 type promoter, a TATA element. A promoter also optionally includes distal enhancer or repressor elements, which can be located as much as several thousand base pairs from the start site of transcription. A “constitutive” promoter is a promoter that is active under most environmental and developmental conditions. An “inducible” promoter is a promoter that is active under environmental or developmental regulation. The term “operably linked” refers to a functional linkage between a nucleic acid expression control sequence (such as a promoter, or array of transcription factor binding sites) and a second nucleic acid sequence, wherein the expression control sequence directs transcription of the nucleic acid corresponding to the second sequence.

[0099] As used herein, “recombinant” refers to a polynucleotide synthesized or otherwise manipulated in vitro (e.g., “recombinant polynucleotide”), to methods of using recombinant polynucleotides to produce gene products in cells or other biological systems, or to a polypeptide (“recombinant protein”) encoded by a recombinant polynucleotide. “Recombinant means” also encompass the ligation of nucleic acids having various coding regions or domains or promoter sequences from different sources into an expression cassette or vector for expression of, e.g., inducible or constitutive expression of a fusion protein comprising a translocation domain of the invention and a nucleic acid sequence amplified using a primer of the invention.

[0100] The phrase “selectively (or specifically) hybridizes to” refers to the binding, duplexing, or hybridizing of a molecule only to a particular nucleotide sequence under stringent hybridization conditions when that sequence is present in a complex mixture (e.g., total cellular or library DNA or RNA).

[0101] The phrase “stringent hybridization conditions” refers to conditions under which a probe will hybridize to its target subsequence, typically in a complex mixture of nucleic acid, but to no other sequences. Stringent conditions are sequence-dependent and will be different in different circumstances. Longer sequences hybridize specifically at higher temperatures. An extensive guide to the hybridization of nucleic acids is found in Tijssen, Techniques in Biochemistry and Molecular Biology—Hybridisation with Nucleic Probes, “Overview of principles of hybridization and the strategy of nucleic acid assays” (1993). Generally, stringent conditions are selected to be about 5-10° C. lower than the thermal melting point (Tm) for the specific sequence at a defined ionic strength pH. The Tm is the temperature (under defined ionic strength, pH, and nucleic concentration) at which 50% of the probes complementary to the target hybridize to the target sequence at equilibrium (as the target sequences are present in excess, at Tm, 50% of the probes are occupied at equilibrium). Stringent conditions will be those in which the salt concentration is less than about 1.0 M sodium ion, typically about 0.01 to 1.0 M sodium ion concentration (or other salts) at pH 7.0 to 8.3 and the temperature is at least about 30° C. for short probes (e.g., 10 to 50 nucleotides) and at least about 60° C. for long probes (e.g., greater than 50 nucleotides). Stringent conditions may also be achieved with the addition of destabilizing agents such as formamide. For selective or specific hybridization, a positive signal is at least two times background, optionally 10 times background hybridization. Exemplary stringent hybridization conditions can be as following: 50% formamide, Sx SSC, and 1% SDS, incubating at 42° C., or, Sx SSC, 1% SDS, incubating at 65° C., with wash in 0.2×SSC, and 0.1% SDS at 65° C. Such hybridizations and wash steps can be carried out for, e.g., 1, 2, 5, 10, 15, 30, 60; or more minutes.

[0102] Nucleic acids that do not hybridize to each other under stringent conditions are still substantially related if the polypeptides which they encode are substantially related. This occurs, for example, when a copy of a nucleic acid is created using the maximum codon degeneracy permitted by the genetic code. In such cases, the nucleic acids typically hybridize under moderately stringent hybridization conditions. Exemplary “moderately stringent hybridization conditions” include a hybridization in a buffer of 40% formamide, 1 M NaCl, 1% SDS at 37° C., and a wash in 1×SSC at 45° C. Such hybridizations and wash steps can be carried out for, e.g., 1, 2, 5, 10, 15, 30, 60, or more minutes. A positive hybridization is at least twice background. Those of ordinary skill will readily recognize that alternative hybridization and wash conditions can be utilized to provide conditions of similar stringency.

[0103] “Antibody” refers to a polypeptide comprising a framework region from an immunoglobulin gene or fragments thereof that specifically binds and recognizes an antigen. The recognized immunoglobulin genes include the kappa, lambda, alpha, gamma, delta, epsilon, and mu constant region genes, as well as the myriad immunoglobulin variable region genes. Light chains are classified as either kappa or lambda. Heavy chains are classified as gamma, mu, alpha, delta, or epsilon, which in turn define the immunoglobulin classes, IgG, IgM, IgA, IgD and IgE, respectively.

[0104] An exemplary immunoglobulin (antibody) structural unit comprises a tetramer. Each tetramer is composed of two identical pairs of polypeptide chains, each pair having one “light” (about 25 kDa) and one “heavy” chain (about 50-70 kDa). The N-terminus of each chain defines a variable region of about 100 to 110 or more amino acids primarily responsible for antigen recognition. The terms variable light chain (VL) and variable heavy chain (VH) refer to these light and heavy chains respectively.

[0105] A “chimeric antibody” is an antibody molecule in which (a) the constant region, or a portion thereof, is altered, replaced or exchanged so that the antigen binding site (variable region) is linked to a constant region of a different or altered class, effector function and/or species, or an entirely different molecule which confers new properties to the chimeric antibody, e.g., an enzyme, toxin, hormone, growth factor, drug, etc.; or (b) the variable region, or a portion thereof, is altered, replaced or exchanged with a variable region having a different or altered antigen specificity.

[0106] An “anti-T1R” antibody is an antibody or antibody fragment that specifically binds a polypeptide encoded by a T1R gene, cDNA, or a subsequence thereof.

[0107] The term “immunoassay” is an assay that uses an antibody to specifically bind an antigen. The immunoassay is characterized by the use of specific binding properties of a particular antibody to isolate, target, and/or quantify the antigen.

[0108] The phrase “specifically (or selectively) binds” to an antibody or, “specifically (or selectively) immunoreactive with,” when referring to a protein or peptide, refers to a binding reaction that is determinative of the presence of the protein in a heterogeneous population of proteins and other biologics. Thus, under designated immunoassay conditions, the specified antibodies bind to a particular protein at least two times the background and do not substantially bind in a significant amount to other proteins present in the sample. Specific binding to an antibody under such conditions may require an antibody that is selected for its specificity for a particular protein. For example, polyclonal antibodies raised to a T1R family member from specific species such as rat, mouse, or human can be selected to obtain only those polyclonal antibodies that are specifically immunoreactive with the T1R polypeptide or an immunogenic portion thereof and not with other proteins, except for orthologs or polymorphic variants and alleles of the T1R polypeptide. This selection may be achieved by subtracting out antibodies that cross-react with T1R molecules from other species or other T1R molecules. Antibodies can also be selected that recognize only T1R GPCR family members but not GPCRs from other families. A variety of immunoassay formats may be used to select antibodies specifically immunoreactive with a particular protein. For example, solid-phase ELISA immunoassays are routinely used to select antibodies specifically immunoreactive with a protein (see, e.g., Harlow & Lane, Antibodies, A Laboratory Manual, (1988), for a description of immunoassay formats and conditions that can be used to determine specific immunoreactivity). Typically a specific or selective reaction will be at least twice background signal or noise and more typically more than 10 to 100 times background.

[0109] The phrase “selectively associates with” refers to the ability of a nucleic acid to “selectively hybridize” with another as defined above, or the ability of an antibody to “selectively (or specifically) bind to a protein, as defined above.

[0110] The term “expression vector” refers to any recombinant expression system for the purpose of expressing a nucleic acid sequence of the invention in vitro or in vivo, constitutively or inducibly, in any cell, including prokaryotic, yeast, fungal, plant, insect or mammalian cell. The term includes linear or circular expression systems. The term includes expression systems that remain episomal or integrate into the host cell genome. The expression systems can have the ability to self-replicate or not, i.e., drive only transient expression in a cell. The term includes recombinant expression “cassettes which contain only the minimum elements needed for transcription of the recombinant nucleic acid.

[0111] By “host cell” is meant a cell that contains an expression vector and supports the replication or expression of the expression vector. Host cells may be prokaryotic cells such as E. coli, or eukaryotic cells such as yeast, insect, amphibian, or mammalian cells such as CHO, HeLa, HEK-293, and the like, e.g., cultured cells, explants, and cells in vivo.

[0112] A. Isolation and Expression of T1R Polypeptides

[0113] Isolation and expression of the T1Rs, or fragments or variants thereof, of the invention can be performed as described below. PCR primers can be used for the amplification of nucleic acids encoding taste receptor ligand-binding regions, and libraries of these nucleic acids can optionally be generated. Individual expression vectors or libraries of expression vectors can then be used to infect or transfect host cells for the functional expression of these nucleic acids or libraries. These genes and vectors can be made and expressed in vitro or in vivo. One of skill will recognize that desired phenotypes for altering and controlling nucleic acid expression can be obtained by modulating the expression or activity of the genes and nucleic acids (e.g., promoters, enhancers and the like) within the vectors of the invention. Any of the known methods described for increasing or decreasing expression or activity can be used. The invention can be practiced in conjunction with any method or protocol known in the art, which are well described in the scientific and patent literature.

[0114] The nucleic acid sequences of the invention and other nucleic acids used to practice this invention, whether RNA, cDNA, genomic DNA, vectors, viruses or hybrids thereof, may be isolated from a variety of sources, genetically engineered, amplified, and/or expressed recombinantly. Any recombinant expression system can be used, including, in addition to mammalian cells, e.g., bacterial, yeast, insect, or plant systems.

[0115] Alternatively, these nucleic acids can be synthesized in vitro by well-known chemical synthesis techniques, as described in, e.g., Carruthers, Cold Spring Harbor Symp. Quant. Biol. 47:411418 (1982); Adams, Am. Chem. Soc. 105:661 (1983); Belousov, Nucleic Acids Res. 25:3440-3444 (1997); Frenkel, Free Radic. Biol. Med. 19:373-380 (1995); Blommers, Biochemistry 33:7886-7896 (1994); Narang, Meth. Enzymol. 68:90 (1979); Brown, Meth. Enzymol. 68:109 (1979); Beaucage, Tetra. Lett. 22:1859 (1981); U.S. Pat. No. 4,458,066. Double-stranded DNA fragments may then be obtained either by synthesizing the complementary strand and annealing the strands together under appropriate conditions, or by adding the complementary strand using DNA polymerase with an appropriate primer sequence.

[0116] Techniques for the manipulation of nucleic acids, such as, for example, for generating mutations in sequences, subcloning, labeling probes, sequencing, hybridization and the like are well described in the scientific and patent literature. See, e.g., Sambrook, ed., Molecular Cloning: a Laboratory manual (2nd ed.), Vols. 1-3, Cold Spring Harbor Laboratory (1989); Current Protocols in Molecular Biology, Ausubel, ed. John Wiley & Sons, Inc., New York (1997); Laboratory Techniques in Biochemistry and Molecular Biology: Hybridization With Nucleic Acid Probes, Part I, Theory and Nucleic Acid Preparation, Tijssen, ed. Elsevier, N.Y. (1993).

[0117] Nucleic acids, vectors, capsids, polypeptides, and the like can be analyzed and quantified by any of a number of general means well known to those of skill in the art. These include, e.g., analytical biochemical methods such as NMR, spectrophotometry, radiography, electrophoresis, capillary electrophoresis, high performance liquid chromatography (HPLC), thin layer chromatography (TLC), and hyperdiffusion chromatography, various immunological methods, e.g., fluid or gel precipitin reactions, immunodiffusion, immunoelectrophoresis, radioimmunoassays (RIAs), enzyme-linked immunosorbent assays (ELISAs), immuno-fluorescent assays, Southern analysis, Northern analysis, dot-blot analysis, gel electrophoresis (e.g., SDS-PAGE), RT-PCR, quantitative PCR, other nucleic acid or target or signal amplification methods, radiolabeling, scintillation counting, and affinity chromatography.

[0118] Oligonucleotide primers may be used to amplify nucleic acid fragments encoding taste receptor ligand-binding regions. The nucleic acids described herein can also be cloned or measured quantitatively using amplification techniques. Amplification methods are also well known in the art, and include, e.g., polymerase chain reaction, PCR(PCR Protocols, a Guide to Methods and Applications, ed. Innis. Academic Press, N.Y. (1990) and PCR Strategies, ed. Innis, Academic Press, Inc., N.Y. (1995), ligase chain reaction (LCR) (see, e.g., Wu, Genomics 4:560 (1989); Landegren, Science 241:1077 (1988); Barringer, Gene 89:117 (1990)); transcription amplification (see, e.g., Kwoh, Proc. Natl. Acad. Sci. USA 86:1173 (1989)); and, self-sustained sequence replication (see, e.g., Guatelli, Proc. Natl. Acad. Sci. USA 87:1874 (1990)); Q Beta replicase amplification (see, e.g., Smith, J. Clin. Microbiol. 35:1477-1491 (1997)); automated Q-beta replicase amplification assay (see, e.g., Burg, Mol. Cell. Probes 10:257-271 (1996)) and other RNA polymerase mediated techniques (e.g., NASBA, Cangene, Mississauga, Ontario); see also Berger, Methods Enzymol. 152:307-316 (1987); Sambrook; Ausubel; U.S. Pat. Nos. 4,683,195 and 4,683,202; Sooknanan, Biotechnology 13:563-564 (1995). The primers can be designed to retain the original sequence of the “donor” 7-membrane receptor. Alternatively, the primers can encode amino acid residues that are conservative substitutions (e.g., hydrophobic for hydrophobic residue, see above discussion) or functionally benign substitutions (e.g., do not prevent plasma membrane insertion, cause cleavage by peptidase, cause abnormal folding of receptor, and the like). Once amplified, the nucleic acids, either individually or as libraries, may be cloned according to methods known in the art, if desired, into any of a variety of vectors using routine molecular biological methods; methods for cloning in vitro amplified nucleic acids are described, e.g., U.S. Pat. No. 5,426,039.

[0119] The primer pairs may be designed to selectively amplify ligand-binding regions of the T1R family members. These regions may vary for different ligands or taste stimuli. Thus, what may be a minimal binding region for one taste stimulus, may be too limiting for a second taste stimulus. Accordingly, ligand-binding regions of different sizes comprising different extracellular domain structures may be amplified.

[0120] Paradigms to design degenerate primer pairs are well known in the art. For example, a COnsensus-DEgenerate Hybrid Oligonucleotide Primer (CODEHOP) strategy computer program is accessible as http://blocks.fhcrc.org/codehop.html, and is directly linked from the BlockMaker multiple sequence alignment site for hybrid primer prediction beginning with a set of related protein sequences, as known taste receptor ligand-binding regions (see, e.g., Rose, Nucleic Acids Res. 26:1628-1635 (1998); Singh, Biotechniques 24:318-319 (1998)).

[0121] Means to synthesize oligonucleotide primer pairs are well known in the art. “Natural” base pairs or synthetic base pairs can be used. For example, use of artificial nucleobases offers a versatile approach to manipulate primer sequence and generate a more complex mixture of amplification products. Various families of artificial nucleobases are capable of assuming multiple hydrogen bonding orientations through internal bond rotations to provide a means for degenerate molecular recognition. Incorporation of these analogs into a single position of a PCR primer allows for generation of a complex library of amplification products. See, e.g., Hoops, Nucleic Acids Res. 25:4866-4871 (1997). Nonpolar molecules can also be used to mimic the shape of natural DNA bases. A non-hydrogen-bonding shape mimic for adenine can replicate efficiently and selectively against a nonpolar shape mimic for thymine (see, e.g., Morales, Nat. Struct. Biol. 5:950-954 (1998)). For example, two degenerate bases can be the pyrimidine base 6H, 8H-3,4-dihydropyrimido[4,5-c][1,2]oxazin-7-one or the purine base N6-methoxy-2,6-diaminopurine (see, e.g., Hill, Proc. Natl. Acad. Sci. USA 95:4258-4263 (1998)). Exemplary degenerate primers of the invention incorporate the nucleobase analog 5′-Dimethoxytrityl-N-benzoyl-2′-deoxy-Cytidine,3′-[(2-cyanoethyl)-(N,N-diisopropyl)]-phosphoramidite (the term “P” in the sequences, see above). This pyrimidine analog hydrogen bonds with purines, including A and G residues.

[0122] Polymorphic variants, alleles, and interspecies homologs that are substantially identical to a taste receptor disclosed herein can be isolated using the nucleic acid probes described above. Alternatively, expression libraries can be used to clone T1R polypeptides and polymorphic variants, alleles, and interspecies homologs thereof, by detecting expressed homologs immunologically with antisera or purified antibodies made against a T1R polypeptide, which also recognize and selectively bind to the T1R homolog.

[0123] Nucleic acids that encode ligand-binding regions of taste receptors may be generated by amplification (e.g., PCR) of appropriate nucleic acid sequences using degenerate primer pairs. The amplified nucleic acid can be genomic DNA from any cell or tissue or mRNA or cDNA derived from taste receptor-expressing cells.

[0124] In one embodiment, hybrid protein-coding sequences comprising nucleic acids encoding T1Rs fused to a translocation sequences may be constructed. Also provided are hybrid T1Rs comprising the translocation motifs and taste stimulus-binding domains of other families of chemosensory receptors, particularly taste receptors. These nucleic acid sequences can be operably linked to transcriptional or translational control elements, e.g., transcription and translation initiation sequences, promoters and enhancers, transcription and translation terminators, polyadenylation sequences, and other sequences useful for transcribing DNA into RNA. In construction of recombinant expression cassettes, vectors, and transgenics, a promoter fragment can be employed to direct expression of the desired nucleic acid in all desired cells or tissues.

[0125] In another embodiment, fusion proteins may include C-terminal or N-terminal translocation sequences. Further, fusion proteins can comprise additional elements, e.g., for protein detection, purification, or other applications. Detection and purification facilitating domains include, e.g., metal chelating peptides such as polyhistidine tracts, histidine-tryptophan modules, or other domains that allow purification on immobilized metals; maltose binding protein; protein A domains that allow purification on immobilized immunoglobulin; or the domain utilized in the FLAGS extension/affinity purification system (Immunex Corp, Seattle Wash.).

[0126] The inclusion of a cleavable linker sequences such as Factor Xa (see, e.g., Ottavi, Biochimie 80:289-293 (1998)), subtilisin protease recognition motif (see, e.g., Polyak, Protein Eng. 10:615-619 (1997)); enterokinase (Invitrogen, San Diego, Calif.), and the like, between the translocation domain (for efficient plasma membrane expression) and the rest of the newly translated polypeptide may be useful to facilitate purification. For example, one construct can include a polypeptide encoding a nucleic acid sequence linked to six histidine residues followed by a thioredoxin, an enterokinase cleavage site (see, e.g., Williams, Biochemistry 34:1787-1797 (1995)), and an C-terminal translocation domain. The histidine residues facilitate detection and purification while the enterokinase cleavage site provides a means for purifying the desired protein(s) from the remainder of the fusion protein. Technology pertaining to vectors encoding fusion proteins and application of fusion proteins are well described in the scientific and patent literature, see, e.g., Kroll, DNA Cell. Biol. 12:441-53 (1993).

[0127] Expression vectors, either as individual expression vectors or as libraries of expression vectors, comprising the ligand-binding domain encoding sequences may be introduced into a genome or into the cytoplasm or a nucleus of a cell and expressed by a variety of conventional techniques, well described in the scientific and patent literature. See, e.g., Roberts, Nature 328:731 (1987); Berger supra; Schneider, Protein Expr. Purif. 6435:10 (1995); Sambrook; Tijssen; Ausubel. Product information from manufacturers of biological reagents and experimental equipment also provide information regarding known biological methods. The vectors can be isolated from natural sources, obtained from such sources as ATCC or GenBank libraries, or prepared by synthetic or recombinant methods.

[0128] The nucleic acids can be expressed in expression cassettes, vectors or viruses which are stably or transiently expressed in cells (e.g., episomal expression systems). Selection markers can be incorporated into expression cassettes and vectors to confer a selectable phenotype on transformed cells and sequences. For example, selection markers can code for episomal maintenance and replication such that integration into the host genome is not required. For example, the marker may encode antibiotic resistance (e.g., chloramphenicol, kanamycin, G418, bleomycin, hygromycin) or herbicide resistance (e.g., chlorosulfuron or Basta) to permit selection of those cells transformed with the desired DNA sequences (see, e.g., Blondelet-Rouault, Gene 190:315-317 (1997); Aubrecht, J. Pharmacol. Exp. Ther. 281:992-997 (1997)). Because selectable marker genes conferring resistance to substrates like neomycin or hygromycin can only be utilized in tissue culture, chemoresistance genes are also used as selectable markers in vitro and in vivo.

[0129] A chimeric nucleic acid sequence may encode a T1R ligand-binding domain within any 7-transmembrane polypeptide. Because 7-transmembrane receptor polypeptides have similar primary sequences and secondary and tertiary structures, structural domains (e.g., extracellular domain, TM domains, cytoplasmic domain, etc.) can be readily identified by sequence analysis. For example, homology modeling, Fourier analysis and helical periodicity detection can identify and characterize the seven domains with a 7-transmembrane receptor sequence. Fast Fourier Transform (FFT) algorithms can be used to assess the dominant periods that characterize profiles of the hydrophobicity and variability of analyzed sequences. Periodicity detection enhancement and alpha helical periodicity index can be done as by, e.g., Donnelly, Protein Sci. 2:55-70 (1993). Other alignment and modeling algorithms are well known in the art, see, e.g., Peitsch, Receptors Channels 4:161-164 (1996); Kyte & Doolittle, J. Md. Bio., 157:105-132 (1982); Cronet, Protein Eng. 6:59-64 (1993) (homology and “discover modeling”); http://bioinfo.weizmann.ac.il/.

[0130] The present invention also includes not only the DNA and proteins having the specified nucleic and amino acid sequences, but also DNA fragments, particularly fragments of, e.g., 40, 60, 80, 100, 150, 200, or 250 nucleotides, or more, as well as protein fragments of, e.g., 10, 20, 30, 50, 70, 100, or 150 amino acids, or more. Optionally, the nucleic acid fragments can encode an antigenic polypeptide which is capable of binding to an antibody raised against a T1R family member. Further, a protein fragment of the invention can optionally be an antigenic fragment which is capable of binding to an antibody raised against a T1R family member.

[0131] Also contemplated are chimeric proteins, comprising at least 10, 20, 30, 50, 70, 100, or 150 amino acids, or more, of one of at least one of the T1R polypeptides described herein, coupled to additional amino acids representing all or part of another GPCR, preferably a member of the 7 transmembrane superfamily. These chimeras can be made from the instant receptors and another GPCR, or they can be made by combining two or more of the present receptors. In one embodiment, one portion of the chimera corresponds tom or is derived from the extracellular domain of a T1R polypeptide of the invention. In another embodiment, one portion of the chimera corresponds to, or is derived from the extracellular domain and one or more of the transmembrane domains of a T1R polypeptide described herein, and the remaining portion or portions can come from another GPCR. Chimeric receptors are well known in the art, and the techniques for creating them and the selection and boundaries of domains or fragments of G protein-coupled receptors for incorporation therein are also well known. Thus, this knowledge of those skilled in the art can readily be used to create such chimeric receptors. The use of such chimeric receptors can provide, for example, a taste selectivity characteristic of one of the receptors specifically disclosed herein, coupled with the signal transduction characteristics of another receptor, such as a well known receptor used in prior art assay systems.

[0132] For example, a domain such as a ligand-binding domain, an extracellular domain, a transmembrane domain, a transmembrane domain, a cytoplasmic domain, an N-terminal domain, a C-terminal domain, or any combination thereof, can be covalently linked to a heterologous protein. For instance, an T1R extracellular domain can be linked to a heterologous GPCR transmembrane domain, or a heterologous GPCR extracellular domain can be linked to a T1R transmembrane domain. Other heterologous proteins of choice can include, e.g., green fluorescent protein, β-gal, glutamtate receptor, and the rhodopsin presequence.

[0133] Also within the scope of the invention are host cells for expressing the T1Rs, fragments, or variants of the invention. To obtain high levels of expression of a cloned gene or nucleic acid, such as cDNAs encoding the T1Rs, fragments, or variants of the invention, one of skill typically subclones the nucleic acid sequence of interest into an expression vector that contains a strong promoter to direct transcription, a transcription/translation terminator, and if for a nucleic acid encoding a protein, a ribosome binding site for translational initiation. Suitable bacterial promoters are well known in the art and described, e.g., in Sambrook et al. However, bacterial or eukaryotic expression systems can be used.

[0134] Any of the well known procedures for introducing foreign nucleotide sequences into host cells may be used. These include the use of calcium phosphate transfection, polybrene, protoplast fusion, electroporation, liposomes, microinjection, plasma vectors, viral vectors and any of the other well known methods for introducing cloned genomic DNA, cDNA, synthetic DNA or other foreign genetic material into a host cell (see, e.g., Sambrook et al.) It is only necessary that the particular genetic engineering procedure used be capable of successfully introducing at lest one nucleic acid molecule into the host cell capable of expressing the T1R, fragment, or variant of interest.

[0135] After the expression vector is introduced into the cells, the transfected cells are cultured under conditions favoring expression of the receptor, fragment, or variant of interest, which is then recovered from the culture using standard techniques. Examples of such techniques are well known in the art. See, e.g., WO 00/06593, which is incorporated by reference in a manner consistent with this disclosure.

[0136] B. Detection of T1R Polypeptides

[0137] In addition to the detection of T1R genes and gene expression using nucleic acid hybridization technology, one can also use immunoassays to detect T1Rs, e.g., to identify taste receptor cells, and variants of T1R family members. Immunoassays can be used to qualitatively or quantitatively analyze the T1Rs. A general overview of the applicable technology can be found in Harlow & Lane, Antibodies: A Laboratory Manual (1988).

[0138] 1. Antibodies to T1R family members

[0139] Methods of producing polyclonal and monoclonal antibodies that react specifically with a T1R family member are known to those of skill in the art (see, e.g., Coligan, Current Protocols in Immunology (1991); Harlow & Lane, supra; Goding, Monoclonal Antibodies: Principles and Practice (2d ed. 1986); and Kohler & Milstein, Nature, 256:495-497 (1975)). Such techniques include antibody preparation by selection of antibodies from libraries of recombinant antibodies in phage or similar vectors, as well as preparation of polyclonal and monoclonal antibodies by immunizing rabbits or mice (see, e.g., Huse et al., Science, 246:1275-1281 (1989); Ward et al., Nature, 341:544-546 (1989)).

[0140] A number of T1R-comprising immunogens may be used to produce antibodies specifically reactive with a T1R family member. For example, a recombinant T1R polypeptide, or an antigenic fragment thereof, can be isolated as described herein. Suitable antigenic regions include, e.g., the consensus sequences that are used to identify members of the T1R family. Recombinant proteins can be expressed in eukaryotic or prokaryotic cells as described above, and purified as generally described above. Recombinant protein is the preferred immunogen for the production of monoclonal or polyclonal antibodies. Alternatively, a synthetic peptide derived from the sequences disclosed herein and conjugated to a carrier protein can be used an immunogen. Naturally occurring protein may also be used either in pure or impure form. The product is then injected into an animal capable of producing antibodies. Either monoclonal or polyclonal antibodies may be generated, for subsequent use in immunoassays to measure the protein.

[0141] Methods of production of polyclonal antibodies are known to those of skill in the art. For example, an inbred strain of mice (e.g., BALB/C mice) or rabbits is immunized with the protein using a standard adjuvant, such as Freund's adjuvant, and a standard immunization protocol. The animal's immune response to the immunogen preparation is monitored by taking test bleeds and determining the titer of reactivity to the T1R. When appropriately high titers of antibody to the immunogen are obtained, blood is collected from the animal and antisera are prepared. Further fractionation of the antisera to enrich for antibodies reactive to the protein can be done if desired (see Harlow & Lane, supra).

[0142] Monoclonal antibodies may be obtained by various techniques familiar to those skilled in the art. Briefly, spleen cells from an animal immunized with a desired antigen may be immortalized, commonly by fusion with a myeloma cell (see Kohler & Milstein, Eur. J. Immunol., 6:511-519 (1976)). Alternative methods of immortalization include transformation with Epstein Barr Virus, oncogenes, or retroviruses, or other methods well known in the art. Colonies arising from single immortalized cells are screened for production of antibodies of the desired specificity and affinity for the antigen, and yield of the monoclonal antibodies produced by such cells may be enhanced by various techniques, including injection into the peritoneal cavity of a vertebrate host. Alternatively, one may isolate DNA sequences which encode a monoclonal antibody or a binding fragment thereof by screening a DNA library from human B cells according to the general protocol outlined by Huse et al., Science, 246:1275-1281 (1989).

[0143] Monoclonal antibodies and polyclonal sera are collected and titered against the immunogen protein in an immunoassay, for example, a solid phase immunoassay with the immunogen immobilized on a solid support. Typically, polyclonal antisera with a titer of 104 or greater are selected and tested for their cross reactivity against non-T1R polypeptides, or even other T1R family members or other related proteins from other organisms, using a competitive binding immunoassay. Specific polyclonal antisera and monoclonal antibodies will usually bind with a Kd of at least about 0.1 mM, more usually at least about 1 pM, optionally at least about 0.1 pM or better, and optionally 0.01 pM or better.

[0144] Once T1R family member specific antibodies are available, individual T1R proteins and protein fragments can be detected by a variety of immunoassay methods. For a review of immunological and immunoassay procedures, see Basic and Clinical Immunology (Stites & Terr eds., 7th ed. 1991). Moreover, the immunoassays of the present invention can be performed in any of several configurations, which are reviewed extensively in Enzyme Immunoassay (Maggio, ed., 1980); and Harlow & Lane, supra.

[0145] 2. Immunological Binding Assays

[0146] T1R proteins, fragments, and variants can be detected and/or quantified using any of a number of well recognized immunological binding assays (see, e.g., U.S. Pat. Nos. 4,366,241; 4,376,110; 4,517,288; and 4,837,168). For a review of the general immunoassays, see also Methods in Cell Biology: Antibodies in Cell Biology, volume 37 (Asai, ed. 1993); Basic and Clinical Immunology (Stites & Terr, eds., 7th ed. 1991). Immunological binding assays (or immunoassays) typically use an antibody that specifically binds to a protein or antigen of choice (in this case a T1R family member or an antigenic subsequence thereof). The antibody (e.g., anti-T1R) may be produced by any of a number of means well known to those of skill in the art and as described above.

[0147] Immunoassays also often use a labeling agent to specifically bind to and label the complex formed by the antibody and antigen. The labeling agent may itself be one of the moieties comprising the antibody/antigen complex. Thus, the labeling agent may be a labeled T1R polypeptide or a labeled anti-T1R antibody. Alternatively, the labeling agent may be a third moiety, such a secondary antibody, that specifically binds to the antibody/T1R complex (a secondary antibody is typically specific to antibodies of the species from which the first antibody is derived). Other proteins capable of specifically binding immunoglobulin constant regions, such as protein A or protein G may also be used as the label agent. These proteins exhibit a strong non-immunogenic reactivity with immunoglobulin constant regions from a variety of species (see, e.g., Kronval et al., J. Immunol., 111:1401-1406 (1973); Akerstrom et al., J. Immunol., 135:2589-2542 (1985)). The labeling agent can be modified with a detectable moiety, such as biotin, to which another molecule can specifically bind, such as streptavidin. A variety of detectable moieties are well known to those skilled in the art.

[0148] Throughout the assays, incubation and/or washing steps may be required after each combination of reagents. Incubation steps can vary from about 5 seconds to several hours, optionally from about 5 minutes to about 24 hours. However, the incubation time will depend upon the assay format, antigen, volume of solution, concentrations, and the like. Usually, the assays will be carried out at ambient temperature, although they can be conducted over a range of temperatures, such as 10° C. to 40° C.

[0149] a. Non-Competitive Assay Formats

[0150] Immunoassays for detecting a T1R polypeptide in a sample may be either competitive or noncompetitive. Noncompetitive immunoassays are assays in which the amount of antigen is directly measured. In one preferred “sandwich” assay, for example, the anti-T1R antibodies can be bound directly to a solid substrate on which they are immobilized. These immobilized antibodies then capture the T1R polypeptide present in the test sample. The T1R polypeptide is thus immobilized is then bound by a labeling agent, such as a second T1R antibody bearing a label. Alternatively, the second antibody may lack a label, but it may, in turn, be bound by a labeled third antibody specific to antibodies of the species from which the second antibody is derived. The second or third antibody is typically modified with a detectable moiety, such as biotin, to which another molecule specifically binds, e.g., streptavidin, to provide a detectable moiety.

[0151] b. Competitive Assay Formats

[0152] In competitive assays, the amount of T1R polypeptide present in the sample is measured indirectly by measuring the amount of a known, added (exogenous) T1R polypeptide displaced (competed away) from an anti-T1R antibody by the unknown T1R polypeptide present in a sample. In one competitive assay, a known amount of T1R polypeptide is added to a sample and the sample is then contacted with an antibody that specifically binds to the T1R. The amount of exogenous T1R polypeptide bound to the antibody is inversely proportional to the concentration of T1R polypeptide present in the sample. In a particularly preferred embodiment, the antibody is immobilized on a solid substrate. The amount of T1R polypeptide bound to the antibody may be determined either by measuring the amount of T1R polypeptide present in a T1R/antibody complex, or alternatively by measuring the amount of remaining uncomplexed protein. The amount of T1R polypeptide may be detected by providing a labeled T1R molecule.

[0153] A hapten inhibition assay is another preferred competitive assay. In this assay the known T1R polypeptide is immobilized on a solid substrate. A known amount of anti-T1R antibody is added to the sample, and the sample is then contacted with the immobilized T1R. The amount of anti-T1R antibody bound to the known immobilized T1R polypeptide is inversely proportional to the amount of T1R polypeptide present in the sample. Again, the amount of immobilized antibody may be detected by detecting either the immobilized fraction of antibody or the fraction of the antibody that remains in solution. Detection may be direct where the antibody is labeled or indirect by the subsequent addition of a labeled moiety that specifically binds to the antibody as described above.

[0154] c. Cross-Reactivity Determinations

[0155] Immunoassays in the competitive binding format can also be used for cross-reactivity determinations. For example, a protein at least partially encoded by the nucleic acid sequences disclosed herein can be immobilized to a solid support. Proteins (e.g., T1R polypeptides and homologs) are added to the assay that compete for binding of the antisera to the immobilized antigen. The ability of the added proteins to compete for binding of the antisera to the immobilized protein is compared to the ability of the T1R polypeptide encoded by the nucleic acid sequences disclosed herein to compete with itself. The percent cross-reactivity for the above proteins is calculated, using standard calculations. Those antisera with less than 10% cross-reactivity with each of the added proteins listed above are selected and pooled. The cross-reacting antibodies are optionally removed from the pooled antisera by immunoabsorption with the added considered proteins, e.g., distantly related homologs. In addition, peptides comprising amino acid sequences representing conserved motifs that are used to identify members of the T1R family can be used in cross-reactivity determinations.

[0156] The immunoabsorbed and pooled antisera are then used in a competitive binding immunoassay as described above to compare a second protein, thought to be perhaps an allele or polymorphic variant of a T1R family member, to the immunogen protein (i.e., T1R polypeptide encoded by the nucleic acid sequences disclosed herein). In order to make this comparison, the two proteins are each assayed at a wide range of concentrations and the amount of each protein required to inhibit 50% of the binding of the antisera to the immobilized protein is determined. If the amount of the second protein required to inhibit 50% of binding is less than 10 times the amount of the protein encoded by nucleic acid sequences disclosed herein required to inhibit 50% of binding, then the second protein is said to specifically bind to the polyclonal antibodies generated to a T1R immunogen.

[0157] Antibodies raised against T1R conserved motifs can also be used to prepare antibodies that specifically bind only to GPCRs of the T1R family, but not to GPCRs from other families.

[0158] Polyclonal antibodies that specifically bind to a particular member of the T1R family can be made by subtracting out cross-reactive antibodies using other T1R family members. Species-specific polyclonal antibodies can be made in a similar way. For example, antibodies specific to human T1R1 can be made by, subtracting out antibodies that are cross-reactive with orthologous sequences, e.g., rat T1R1 or mouse T1R1.

[0159] d. Other Assay Formats

[0160] Western blot (immunoblot) analysis is used to detect and quantify the presence of T1R polypeptide in the sample. The technique generally comprises separating sample proteins by gel electrophoresis on the basis of molecular weight, transferring the separated proteins to a suitable solid support, (such as a nitrocellulose filter, a nylon filter, or derivatized nylon filter), and incubating the sample with the antibodies that specifically bind the T1R polypeptide. The anti-T1R polypeptide antibodies specifically bind to the T1R polypeptide on the solid support. These antibodies may be directly labeled or alternatively may be subsequently detected using labeled antibodies (e.g., labeled sheep anti-mouse antibodies) that specifically bind to the anti-T1R antibodies.

[0161] Other, assay formats include liposome immunoassays (LIA), which use liposomes designed to bind specific molecules (e.g., antibodies) and release encapsulated reagents or markers. The released chemicals are then detected according to standard techniques (see Monroe et al., Amer. Clin. Prod. Rev., 5:34-41 (1986)).

[0162] e. Reduction of Non-Specific Binding

[0163] One of skill in the art will appreciate that it is often desirable to minimize non-specific binding in immunoassays. Particularly, where the assay involves an antigen or antibody immobilized on a solid substrate it is desirable to minimize the amount of non-specific binding to the substrate. Means of reducing such non-specific binding are well known to those of skill in the art. Typically, this technique involves coating the substrate with a proteinaceous composition. In particular, protein compositions such as bovine serum albumin (BSA), nonfat powdered milk, and gelatin are widely used with powdered milk being most preferred.

[0164] f. Labels

[0165] The particular label or detectable group used in the assay is not a critical aspect of the invention, as long as it does not significantly interfere with the specific binding of the antibody used in the assay. The detectable group can be any material having a detectable physical or chemical property. Such detectable labels have been well developed in the field of immunoassays and, in general, most any label useful in such methods can be applied to the present invention. Thus, a label is any composition detectable by spectroscopic, photochemical, biochemical, immunochemical, electrical, optical, or chemical means. Useful labels in the present invention include magnetic beads (e.g., DYNABEADSTM), fluorescent dyes (e.g., fluorescein isothiocyanate, Texas red, rhodamine, and the like), radiolabels (e.g., 3H, 1251, 3sS, 14C, or ³²P), enzymes (e.g., horseradish peroxidase, alkaline phosphatase and others commonly used in an ELISA), and calorimetric labels such as colloidal gold or colored glass or plastic beads (e.g., polystyrene, polypropylene, latex, etc.).

[0166] The label may be coupled directly or indirectly to the desired component of the assay according to methods well known in the art. As indicated above, a wide variety of labels may be used, with the choice of label depending on sensitivity required, ease of conjugation with the compound, stability requirements, available instrumentation, and disposal provisions.

[0167] Non-radioactive labels are often attached by indirect means. Generally, a ligand molecule (e.g., biotin) is covalently bound to the molecule. The ligand then binds to another molecules (e.g., streptavidin) molecule, which is either inherently detectable or covalently bound to a signal system, such as a detectable enzyme, a fluorescent compound, or a chemiluminescent compound. The ligands and their targets can be used in any suitable combination with antibodies that recognize a T1R polypeptide, or secondary antibodies that recognize anti-T1R.

[0168] The molecules can also be conjugated directly to signal generating compounds, e.g., by conjugation with an enzyme or fluorophore. Enzymes of interest as labels will primarily be hydrolases, particularly phosphatases, esterases and glycosidases, or oxidotases, particularly peroxidases. Fluorescent compounds include fluorescein and its derivatives, rhodamine and its derivatives, dansyl, umbelliferone, etc. Chemiluminescent compounds include luciferin, and 2,3-dihydrophthalazinediones, e.g., luminol. For a review of various labeling or signal producing systems that may be used, see U.S. Pat. No. 4,391,904.

[0169] Means of detecting labels are well known to those of skill in the art. Thus, for example, where the label is a radioactive label, means for detection include a scintillation counter or photographic film as in autoradiography. Where the label is a fluorescent label, it may be detected by exciting the fluorochrome with the appropriate wavelength of light and detecting the resulting fluorescence. The fluorescence may be detected visually, by means of photographic film, by the use of electronic detectors such as charge-coupled devices (CCDs) or photomultipliers and the like. Similarly, enzymatic labels may be detected by providing the appropriate substrates for the enzyme and detecting the resulting reaction product. Finally simple calorimetric labels may be detected simply by observing the color associated with the label. Thus, in various dipstick assays, conjugated gold often appears pink, while various conjugated beads appear the color of the bead.

[0170] Some assay formats do not require the use of labeled components. For instance, agglutination assays can be used to detect the presence of the target antibodies. In this case, antigen-coated particles are agglutinated by samples comprising the target antibodies. In this format, none of the components need be labeled and the presence of the target antibody is detected by simple visual inspection.

[0171] C. Detection of Modulators

[0172] Compositions and methods for determining whether a test compound specifically binds to a chemosensory receptor of the invention, both in vitro and in vivo, are described below. Many aspects of cell physiology can be monitored to assess the effect of ligand binding to a T1R polypeptide of the invention. These assays may be performed on intact cells expressing a chemosensory receptor, on permeabilized cells, or on membrane fractions produced by standard methods.

[0173] Taste receptors bind taste stimuli and initiate the transduction of chemical stimuli into electrical signals. An activated or inhibited G protein will in turn alter the properties of target enzymes, channels, and other effector proteins. Some examples are the activation of cGMP phosphodiesterase by transducin in the visual system, adenylate cyclase by the stimulatory G protein, phospholipase C by Gq and other cognate G proteins, and modulation of diverse channels by Gi and other G proteins. Downstream consequences can also be examined such as generation of diacyl glycerol and IP3 by phospholipase C, and in turn, for calcium mobilization by IP3.

[0174] The T1R proteins or polypeptides of the assay will typically be selected from a polypeptide having a sequence of SEQ ID NOS: 4, 10, 12, 14, 17, 21 or fragments or conservatively modified variants thereof. Optionally, the fragments and variants can be antigenic fragments and variants which bind to an anti-T1R antibody.

[0175] Alternatively, the T1R proteins or polypeptides of the assay can be derived from a eukaryote host cell and can include an amino acid subsequence having amino acid sequence identity to SEQ ID NOS: 4, 10, 12, 14, 17, 21, or fragments or conservatively modified variants thereof. Generally, the amino acid sequence identity will be at least 35 to 50%, or optionally 75%, 85%, 90%, 95%, 96%, 97%, 98%, or 99%. Optionally, the T1R proteins or polypeptides of the assays can comprise a domain of a T1R protein, such as an extracellular domain, transmembrane region, transmembrane domain, cytoplasmic domain, ligand-binding domain, and the like. Further, as described above, the T1R protein or a domain thereof can be covalently linked to a heterologous protein to create a chimeric protein used in the assays described herein.

[0176] Modulators of T1R receptor activity are tested using T1R proteins or polypeptides as described above, either recombinant or naturally occurring. The T1R proteins or polypeptides can be isolated, expressed in a cell, expressed in a membrane derived from a cell, expressed in tissue or in an animal, either recombinant or naturally occurring. For example, tongue slices, dissociated cells from a tongue, transformed cells, or membranes can be used. Modulation can be tested using one of the in vitro or in vivo assays described herein.

[0177] 1. In Vitro Binding Assays

[0178] Taste transduction can also be examined in vitro with soluble or solid state reactions, using a T1R polypeptide of the invention. In a particular embodiment, a T1R ligand-binding domain can be used in vitro in soluble or solid state reactions to assay for ligand binding.

[0179] For instance, the T1R N-terminal domain is predicted to be involved in ligand binding. More particularly, the T1Rs belong to a GPCR sub-family that is characterized by large, approximately 600 amino acid, extracellular N-terminal segments. These N-terminal segments are thought to form, at least in part, the ligand-binding domains, and are therefore useful in biochemical assays to identify T1R agonists and antagonists. The ligand-binding domain may also contain additional portions of the extracellular domain, such as the extracellular loops of the transmembrane domain. Similar assays have been used with other GPCRs that are related to the T1Rs, such as the metabotropic glutamate receptors (see, e.g., Han and Hampson, J. Biol. Chem. 274:10008-10013 (1999)). These assays might involve displacing a radioactively or fluorescently labeled ligand, measuring changes in intrinsic fluorescence or changes in proteolytic susceptibility, etc.

[0180] Ligand binding to a T1R polypeptide of the invention can be tested in solution, in a bilayer membrane, optionally attached to a solid phase, in a lipid monolayer, or in vesicles. Binding of a modulator can be tested using, e.g., changes in spectroscopic characteristics (e.g., fluorescence, absorbance, refractive index) hydrodynamic (e.g., shape), chromatographic, or solubility properties. Preferred binding assays of the invention are biochemical binding assays that use recombinant soluble N-terminal T1R domains.

[0181] Receptor-G protein interactions can also be examined. For example, binding of the G protein to the receptor, or its release from the receptor can be examined. More particularly, in the absence of GTP, an activator will lead to the formation of a tight complex of a G protein (all three subunits) with the receptor. This complex can be detected in a variety of ways, as noted above. Such an assay can be modified to search for inhibitors, e.g., by adding an activator to the receptor and G protein in the absence of GTP, which form a tight complex, and then screen for inhibitors by looking at dissociation of the receptor-G protein complex. In the presence of GTP, release of the alpha subunit of the G protein from the other two G protein subunits serves as a criterion of activation. An activated or inhibited G protein will in turn alter the properties of target enzymes, channels, and other effector proteins.

[0182] In another embodiment of the invention, a GTPγS assay may be used. As described above, upon activation of a GPCR, the Ga subunit of the G protein complex is stimulated to exchange bound GDP for GTP. Ligand-mediated stimulation of G protein exchange activity can be measured in a biochemical assay measuring the binding of added radioactively-labeled GTPγ³⁵S to the G protein in the presence of a putative ligand. Typically, membranes containing the chemosensory receptor of interest are mixed with a complex of G proteins. Potential inhibitors and/or activators and GTPγS are added to the assay, and binding of GTPγS to the G protein is measured. Binding can be measured by liquid scintillation counting or by any other means known in the art, including scintillation proximity assays (SPA). In other assays formats, fluorescently-labeled GTPγS can be utilized.

[0183] 2. Fluorescence Polarization Assays

[0184] In another embodiment, Fluorescence Polarization (“FP”) based assays may be used to detect and monitor ligand binding. Fluorescence polarization is a versatile laboratory technique for measuring equilibrium binding, nucleic acid hybridization, and enzymatic activity. Fluorescence polarization assays are homogeneous in that they do not require a separation step such as centrifugation, filtration, chromatography, precipitation, or electrophoresis. These assays are done in real time, directly in solution and do not require an immobilized phase. Polarization values can be measured repeatedly and after the addition of reagents since measuring the polarization is rapid and does not destroy the sample. Generally, this technique can be used to measure polarization values of fluorophores from low picomolar to micromolar levels. This section describes how fluorescence polarization can be used in a simple and quantitative way to measure the binding of ligands to the T1R polypeptides of the invention.

[0185] When a fluorescently labeled molecule is excited with plane polarized light, it emits light that has a degree of polarization that is inversely proportional to its molecular rotation. Large fluorescently labeled molecules remain relatively stationary during the excited state (4 nanoseconds in the case of fluorescein) and the polarization of the light remains relatively constant between excitation and emission. Small fluorescently labeled molecules rotate rapidly during the excited state and the polarization changes significantly between excitation and emission. Therefore, small molecules have low polarization values and large molecules have high polarization values. For example, a single-stranded fluorescein-labeled oligonucleotide has a relatively low polarization value but when it is hybridized to a complementary strand, it has a higher polarization value. When using FP to detect and monitor taste stimulus-binding which may activate or inhibit the chemosensory receptors of the invention, fluorescence-labeled taste stimuli or auto-fluorescent taste stimuli may be used.

[0186] Fluorescence polarization (P) is defined as: $P = \frac{{Int}_{\coprod} - {int}_{\bot}}{{Int}_{\coprod} + {int}_{\bot}}$

[0187] Where Π is the intensity of the emission light parallel to the excitation light plane and Int ⊥ is the intensity of the emission light perpendicular to the excitation light plane. P, being a ratio of light intensities, is a dimensionless number. For example, the Beacon® and Beacon 2000™ System may be used in connection with these assays. Such systems typically express polarization in millipolarization units (1 Polarization Unit=1000 mP Units).

[0188] The relationship between molecular rotation and size is described by the Perrin equation and the reader is referred to Jolley, M. E. (1991) in Journal of Analytical Toxicology, pp. 236-240, which gives a thorough explanation of this equation. Summarily, the Perrin equation states that polarization is directly proportional to the rotational relaxation time, the time that it takes a molecule to rotate through an angle of approximately 68.50 Rotational relaxation time is related to viscosity (η), absolute temperature (T), molecular volume (V), and the gas constant (R) by the following equation: ${{Rotational}\quad {Relaxation}\quad {Time}} = \frac{3\quad \eta \quad V}{RT}$

[0189] The rotational relaxation time is small (≈1 nanosecond) for small molecules (e.g. fluorescein) and large (≈100 nanoseconds) for large molecules (e.g. immunoglobulins). If viscosity and temperature are held constant, rotational relaxation time, and therefore polarization, is directly related to the molecular volume. Changes in molecular volume may be due to interactions with other molecules, dissociation, polymerization, degradation, hybridization, or conformational changes of the fluorescently labeled molecule. For example, fluorescence polarization has been used to measure enzymatic cleavage of large fluorescein labeled polymers by proteases, DNases, and RNases. It also has been used to measure equilibrium binding for protein/protein interactions, antibody/antigen binding, and protein/DNA binding.

[0190] 3. Solid State and Soluble High Throughput Assays

[0191] In yet another embodiment, the invention provides soluble assays using a T1R polypeptide; or a cell or tissue expressing an T1R polypeptide. In another embodiment, the invention provides solid phase based in vitro assays in a high throughput format, where the T1R polypeptide, or cell or tissue expressing the T1R polypeptide is attached to a solid phase substrate.

[0192] In the high throughput assays of the invention, it is possible to screen up to several thousand different modulators or ligands in a single day. In particular, each well of a microtiter plate can be used to run a separate assay against a selected potential modulator, or, if concentration or incubation time effects are to be observed, every 5-10 wells can test a single modulator. Thus, a single standard microtiter plate can assay about 100 (e.g., 96) modulators. If 1536 well plates are used, then a single plate can easily assay from about 1000 to about 1500 different compounds. It is also possible to assay multiple compounds in each plate well. It is possible to assay several different plates per day; assay screens for up to about 6,000-20,000 different compounds is possible using the integrated systems of the invention. More recently, microfluidic approaches to reagent manipulation have been developed.

[0193] The molecule of interest can be bound to the solid state component, directly or indirectly, via covalent or non-covalent linkage, e.g., via a tag. The tag can be any of a variety of components. In general, a molecule which binds the tag (a tag binder) is fixed to a solid support, and the tagged molecule of interest (e.g., the taste transduction molecule of interest) is attached to the solid support by interaction of the tag and the tag binder.

[0194] A number of tags and tag binders can be used, based upon known molecular interactions well described in the literature. For example, where a tag has a natural binder, for example, biotin, protein A, or protein G, it can be used in conjunction with appropriate tag binders (avidin, streptavidin, neutravidin, the Fc region of an immunoglobulin, etc.). Antibodies to molecules with natural binders such as biotin are also widely available and appropriate tag binders (see, SIGMA Immunochemicals 1998 catalogue SIGMA, St. Louis Mo.).

[0195] Similarly, any haptenic or antigenic compound can be used in combination with an appropriate antibody to form a tag/tag binder pair. Thousands of specific antibodies are commercially available and many additional antibodies are described in the literature. For example, in one common configuration, the tag is a first antibody and the tag binder is a second antibody which recognizes the first antibody. In addition to antibody-antigen interactions, receptor-ligand interactions are also appropriate as tag and tag-binder pairs. For example, agonists and antagonists of cell membrane receptors (e.g., cell receptor-ligand interactions such as transferrin, c-kit, viral receptor ligands, cytokine receptors, chemokine receptors, interleukin receptors, immunoglobulin receptors and antibodies, the cadherein family, the integrin family, the selectin family, and the like; see, e.g., Pigott & Power, The Adhesion Molecule Facts Book I (1993)). Similarly, toxins and venoms, viral epitopes, hormones (e.g., opiates, steroids, etc.), intracellular receptors (e.g., which mediate the effects of various small ligands, including steroids, thyroid hormone, retinoids and vitamin D; peptides), drugs, lectins, sugars, nucleic acids (both linear and cyclic polymer configurations), oligosaccharides, proteins, phospholipids and antibodies can all interact with various cell receptors.

[0196] Synthetic polymers, such as polyurethanes, polyesters, polycarbonates, polyureas, polyamides, polyethyleneimines, polyarylene sulfides, polysiloxanes, polyimides, and polyacetates can also form an appropriate tag or tag binder. Many other tag/tag binder pairs are also useful in assay systems described herein, as would be apparent to one of skill upon review of this disclosure.

[0197] Common linkers such as peptides, polyethers, and the like can also serve as tags, and include polypeptide sequences, such as poly gly sequences of between about 5 and 200 amino acids. Such flexible linkers are known to persons of skill in the art. For example, poly(ethelyne glycol) linkers are available from Shearwater Polymers, Inc. Huntsville, Ala. These linkers optionally have amide linkages, sulfhydryl linkages, or heterofunctional linkages.

[0198] Tag binders are fixed to solid substrates using any of a variety of methods currently available. Solid substrates are commonly derivatized or functionalized by exposing all or a portion of the substrate to a chemical reagent which fixes a chemical group to the surface which is reactive with a portion of the tag binder. For example, groups which are suitable for attachment to a longer chain portion would include amines, hydroxyl, thiol, and carboxyl groups. Aminoalkylsilanes and hydroxyalkylsilanes can be used to functionalize a variety of surfaces, such as glass surfaces. The construction of such solid phase biopolymer arrays is well described in the literature. See, e.g., Merrifield, J. Am. Chem. Soc., 85:2149-2154 (1963) (describing solid phase synthesis of, e.g., peptides); Geysen et al., J. Immun. Meth., 102:259-274 (1987) (describing synthesis of solid phase components on pins); Frank & Doring, Tetrahedron, 44:60316040 (1988) (describing synthesis of various peptide sequences on cellulose disks); Fodor et al., Science, 251:767-777 (1991); Sheldon et al., Clinical Chemistry, 39(4):718-719 (1993); and Kozal et al., Nature Medicine, 2(7):753759 (1996) (all describing arrays of biopolymers fixed to solid substrates). Non-chemical approaches for fixing tag binders to substrates include other common methods, such as heat, cross-linking by UV radiation, and the like.

[0199] 4. Computer-Based Assays

[0200] Yet another assay for compounds that modulate T1R polypeptide activity involves computer assisted compound design, in which a computer system is used to generate a three-dimensional structure of an T1R polypeptide based on the structural information encoded by its amino acid sequence. The input amino acid sequence interacts directly and actively with a preestablished algorithm in a computer program to yield secondary, tertiary, and quaternary structural models of the protein. The models of the protein structure are then examined to identify regions of the structure that have the ability to bind, e.g., ligands. These regions are then used to identify ligands that bind to the protein.

[0201] The three-dimensional structural model of the protein is generated by entering protein amino acid sequences of at least 10 amino acid residues or corresponding nucleic acid sequences encoding a T1R polypeptide into the computer system. The nucleotide sequence encoding the T1R polypeptide, or the amino acid sequence thereof, can be any sequence disclosed herein, and conservatively modified versions thereof.

[0202] The amino acid sequence represents the primary sequence or subsequence of the protein, which encodes the structural information of the protein. At least 10 residues of the amino acid sequence (or a nucleotide sequence encoding 10 amino acids) are entered into the computer system from computer keyboards, computer readable substrates that include, but are not limited to, electronic storage media (e.g., magnetic diskettes, tapes, cartridges, and chips), optical media (e.g., CD ROM), information distributed by internet sites, and by RAM. The three-dimensional structural model of the protein is then generated by the interaction of the amino acid sequence and the computer system, using software known to those of skill in the art.

[0203] The amino acid sequence represents a primary structure that encodes the information necessary to form the secondary, tertiary and quaternary structure of the protein of interest. The software looks at certain parameters encoded by the primary sequence to generate the structural model. These parameters are referred to as “energy terms,” and primarily include electrostatic potentials, hydrophobic potentials, solvent accessible surfaces, and hydrogen bonding. Secondary energy terms include van der Waals potentials. Biological molecules form the structures that minimize the energy terms in a cumulative fashion. The computer program is therefore using these terms encoded by the primary structure or amino acid sequence to create the secondary structural model.

[0204] The tertiary structure of the protein encoded by the secondary structure is then formed on the basis of the energy terms of the secondary structure. The user at this point can enter additional variables such as whether the protein is membrane bound or soluble, its location in the body, and its cellular location, e.g., cytoplasmic, surface, or nuclear. These variables along with the energy terms of the secondary structure are used to form the model of the tertiary structure. In modeling the tertiary structure, the computer program matches hydrophobic faces of secondary structure with like, and hydrophilic faces of secondary structure with like.

[0205] Once the structure has been generated, potential ligand-binding regions are identified by the computer system. Three-dimensional structures for potential ligands are generated by entering amino acid or nucleotide sequences or chemical formulas of compounds, as described above. The three-dimensional structure of the potential ligand is then compared to that of the T1R polypeptide to identify ligands that bind to the protein. Binding affinity between the protein and ligands is determined using energy terms to determine which ligands have an enhanced probability of binding to the protein.

[0206] Computer systems are also used to screen for mutations, polymorphic variants, alleles, and interspecies homologs of T1R genes. Such mutations can be associated with disease states or genetic traits. As described above, GeneChip™ and related technology can also be used to screen for mutations, polymorphic variants, alleles, and interspecies homologs. Once the variants are identified, diagnostic assays can be used to identify patients having such mutated genes. Identification of the mutated T1R genes involves receiving input of a first nucleic acid or amino acid sequence of a T1R gene, or conservatively modified versions thereof. The sequence is entered into the computer system as described above. The first nucleic acid or amino acid sequence is then compared to a second nucleic acid or amino acid sequence that has substantial identity to the first sequence. The second sequence is entered into the computer system in the manner described above. Once the first and second sequences are compared, nucleotide or amino acid differences between the sequences are identified. Such sequences can represent allelic differences in various T1R genes, and mutations associated with disease states and genetic traits.

[0207] 5. Cell-Based Binding Assays

[0208] In one embodiment, a T1R protein or polypeptide is expressed in a eukaryotic cell as a chimeric receptor with a heterologous, chaperone sequence that facilitates its maturation and targeting through the secretory pathway. Such chimeric T1R polypeptides can be expressed in any eukaryotic cell, such as HEK-293 cells. Preferably, the cells comprise a functional G protein, e.g., Gα15, that is capable of coupling the chimeric receptor to an intracellular signaling pathway or to a signaling protein such as phospholipase C. Activation of such chimeric receptors in such cells can be detected using any standard method, such as by detecting changes in intracellular calcium by detecting FURA-2 dependent fluorescence in the cell.

[0209] Activated GPCR receptors become substrates for kinases that phosphorylate the C-terminal tail of the receptor (and possibly other sites as well). Thus, activators will promote the transfer of 32P from gamma-labeled GTP to the receptor, which can be assayed with a scintillation counter. The phosphorylation of the C-terminal tail will promote the binding of arrestin-like proteins and will interfere with the binding of G proteins. The kinase/arrestin pathway plays a key role in the desensitization of many GPCR receptors. For example, compounds that modulate the duration a taste receptor stays active would be useful as a means of prolonging a desired taste or cutting off an unpleasant one. For a general review of GPCR signal transduction and methods of assaying signal transduction, see, e.g., Methods in Enzymology, vols. 237 and 238 (1994) and volume 96 (1983); Bourne et al., Nature, 10:349:117-27 (1991); Bourne et al., Nature, 348:125-32 (1990); Pitcher et al., Annu. Rev. Biochem., 67:653-92 (1998).

[0210] T1R modulation may be assayed by comparing the response of a T1R polypeptide treated with a putative T1R modulator to the response of an untreated control sample. Such putative T1R modulators can include taste stimuli that either inhibit or activate T1R polypeptide activity. In one embodiment, control samples (untreated with activators or inhibitors) are assigned a relative T1R activity value of 100. Inhibition of a T1R polypeptide is achieved when the T1R activity value relative to the control is about 90%, optionally 50%, optionally 25-0%. Activation of a T1R polypeptide is achieved when the T1R activity value relative to the control is 110%, optionally 150%, 200-500%, or 1000-2000%.

[0211] Changes in ion flux may be assessed by determining changes in ionic polarization (i.e., electrical potential) of the cell or membrane expressing a T1R polypeptide. One means to determine changes in cellular polarization is by measuring changes in current (thereby measuring changes in polarization) with voltage-clamp and patch-clamp techniques (see, e.g., the “cell-attached” mode, the “inside-out” mode, and the “whole cell” mode, e.g., Ackerman et al., New Engl. J. Med., 336:1575-1595 (1997)). Whole cell currents are conveniently determined using the standard. Other known assays include: radiolabeled ion flux assays and fluorescence assays using voltage-sensitive dyes (see, e.g., Vestergarrd-Bogind et al., J. Membrane Biol., 88:67-75 (1988); Gonzales & Tsien, Chem. Biol., 4:269-277 (1997); Daniel et al., J. Pharmacol. Meth., 25:185-193 (1991); Holevinsky et al., J. Membrane Biology, 137:59-70 (1994)). Generally, the compounds to be tested are present in the range from 1 pM to 100 mM.

[0212] The effects of the test compounds upon the function of the polypeptides can be measured by examining any of the parameters described above. Any suitable physiological change that affects GPCR activity can be used to assess the influence of a test compound on the polypeptides of this invention. When the functional consequences are determined using intact cells or animals, one can also measure a variety of effects such as transmitter release, hormone release, transcriptional changes to both known and uncharacterized genetic markers (e.g., northern blots), changes in cell metabolism such as cell growth or pH changes, and changes in intracellular second messengers such as Ca²⁺, IP3, cGMP, or cAMP.

[0213] Preferred assays for GPCRs include cells that are loaded with ion or voltage sensitive dyes to report receptor activity. Assays for determining activity of such receptors can also use known agonists and antagonists for other G protein-coupled receptors as negative or positive controls to assess activity of tested compounds. In assays for identifying modulatory compounds (e.g., agonists, antagonists), changes in the level of ions in the cytoplasm or membrane voltage will be monitored using an ion sensitive or membrane voltage fluorescent indicator, respectively. Among the ion-sensitive indicators and voltage probes that may be employed are those disclosed in the Molecular Probes 1997 Catalog. For G protein-coupled receptors, promiscuous G proteins such as Gα15 and Gα16 can be used in the assay of choice (Wilkie et al., Proc. Nat'l Acad. Sci., 88:10049-10053 (1991)). Such promiscuous G proteins allow coupling of a wide range of receptors.

[0214] Receptor activation typically initiates subsequent intracellular events, e.g., increases in second messengers such as IP3, which releases intracellular stores of calcium ions. Activation of some G protein-coupled receptors stimulates the formation of inositol triphosphate (IP3) through phospholipase C-mediated hydrolysis of phosphatidylinositol (Berridge & Irvine, Nature, 312:315-21 (1984)). IP3 in turn stimulates the release of intracellular calcium ion stores. Thus, a change in cytoplasmic calcium ion levels, or a change in second messenger levels such as IP3 can be used to assess G protein-coupled receptor function. Cells expressing such G protein-coupled receptors may exhibit increased cytoplasmic calcium levels as a result of contribution from both intracellular stores and via activation of ion channels, in which case it may be desirable although not necessary to conduct such assays in calcium-free buffer, optionally supplemented with a chelating agent such as EGTA, to distinguish fluorescence response resulting from calcium release from internal stores.

[0215] Other assays can involve determining the activity of receptors which, when activated, result in a change in the level of intracellular cyclic nucleotides, e.g., cAMP or cGMP, by activating or inhibiting enzymes such as adenylate cyclase. There are cyclic nucleotide-gated ion channels, e.g., rod photoreceptor cell channels and olfactory neuron channels that are permeable to cations upon activation by binding of cAMP or cGMP (see, e.g., Altenhofen et al., Proc. Nat'l Acad. Sci., 88:9868-9872 (1991) and Dhallan et al., Nature, 347:184-187 (1990)). In cases where activation of the receptor results in a decrease in cyclic nucleotide levels, it may be preferable to expose the cells to agents that increase intracellular cyclic nucleotide levels, e.g., forskolin, prior to adding a receptor-activating compound to the cells in the assay. Cells for this type of assay can be made by co-transfection of a host cell with DNA encoding a cyclic nucleotide-crated ion channel, GPCR phosphatase and DNA encoding a receptor (e.g., certain glutamate receptors, muscarinic acetylcholine receptors, dopamine receptors, serotonin receptors, and the like), which, when activated, causes a change in cyclic nucleotide levels in the cytoplasm.

[0216] In a preferred embodiment, T1R polypeptide activity is measured by expressing a T1R gene in a heterologous cell with a promiscuous G protein that links the receptor to a phospholipase C signal transduction pathway (see Offermanns & Simon, J. Biol. Chem., 270:15175-15180 (1995)). Optionally the cell line is HEK-293 (which does not naturally express T1R genes) and the promiscuous G protein is Gα15 (Offermanns & Simon, supra). Modulation of taste transduction is assayed by measuring changes in intracellular Ca²⁺ levels, which change in response to modulation of the T1R signal transduction pathway via administration of a molecule that associates with a T1R polypeptide. Changes in Ca²⁺ levels are optionally measured using fluorescent Ca²⁺ indicator dyes and fluorometric imaging.

[0217] In one embodiment, the changes in intracellular cAMP or cGMP can be measured using immunoassays. The method described in Offermanns & Simon, J. Bio. Chem., 270:15175-15180 (1995), may be used to determine the level of cAMP. Also, the method described in Felley-Bosco et al., Am. J. Resp. Cell and Mol. Biol., 11:159-164 (1994), may be used to determine the level of cGMP. Further, an assay kit for measuring cAMP and/or cGMP is described in U.S. Pat. No. 4,115,538, herein incorporated by reference.

[0218] In another embodiment, phosphatidyl inositol (PI) hydrolysis can be analyzed according to U.S. Pat. No. 5,436,128, herein incorporated by reference. Briefly, the assay involves labeling of cells with 3H-myoinositol for 48 or more hrs. The labeled cells are treated with a test compound for one hour. The treated cells are lysed and extracted in chloroform-methanol-water after which the inositol phosphates were separated by ion exchange chromatography and quantified by scintillation counting. Fold stimulation is determined by calculating the ratio of cpm in the presence of agonist, to cpm in the presence of buffer control. Likewise, fold inhibition is determined by calculating the ratio of cpm in the presence of antagonist, to cpm in the presence of buffer control (which may or may not contain an agonist).

[0219] In another embodiment, transcription levels can be measured to assess the effects of a test compound on signal transduction. A host cell containing a T1R polypeptide of interest is contacted with a test compound for a sufficient time to effect any interactions, and then the level of gene expression is measured. The amount of time to effect such interactions may be empirically determined, such as by running a time course and measuring the level of transcription as a function of time. The amount of transcription may be measured by using any method known to those of skill in the art to be suitable. For example, mRNA expression of the protein of interest may be detected using northern blots or their polypeptide products may be identified using immunoassays. Alternatively, transcription based assays using reporter gene may be used as described in U.S. Pat. No. 5,436,128, herein incorporated by reference. The reporter genes can be, e.g., chloramphenicol acetyltransferase, luciferase, ′3-galactosidase and alkaline phosphatase. Furthermore, the protein of interest can be used as an indirect reporter via attachment to a second reporter such as green fluorescent protein (see, e.g., Mistili & Spector, Nature Biotechnology, 15:961-964 (1997)).

[0220] The amount of transcription is then compared to the amount of transcription in either the same cell in the absence of the test compound, or it may be compared with the amount of transcription in a substantially identical cell that lacks the T1R polypeptide of interest. A substantially identical cell may be derived from the same cells from which the recombinant cell was prepared but which had not been modified by introduction of heterologous DNA. Any difference in the amount of transcription indicates that the test compound has in some manner altered the activity of the T1R polypeptide of interest.

[0221] 6. Transgenic Non-Human Animals Expressing Chemosensory Receptors

[0222] Non-human animals expressing one or more chemosensory receptor sequences of the invention, can also be used for receptor assays. Such expression can be used to determine whether a test compound specifically binds to a mammalian taste transmembrane receptor polypeptide in vivo by contacting a non-human animal stably or transiently transfected with a nucleic acid encoding a chemosensory receptor or ligand-binding region thereof with a test compound and determining whether the animal reacts to the test compound by specifically binding to the receptor polypeptide.

[0223] Animals transfected or infected with the vectors of the invention are particularly useful for assays to identify and characterize taste stimuli/ligands that can bind to a specific or sets of receptors. Such vector-infected animals expressing human chemosensory receptor sequences can be used for in vivo screening of taste stimuli and their effect on, e.g., cell physiology (e.g., on taste neurons), on the CNS, or behavior.

[0224] Means to infect/express the nucleic acids and vectors, either individually or as libraries, are well known in the art. A variety of individual cell, organ, or whole animal parameters can be measured by a variety of means. The T1R sequences of the invention can be for example expressed in animal taste tissues by delivery with an infecting agent, e.g., adenovirus expression vector.

[0225] The endogenous chemosensory receptor genes can remain functional and wild-type (native) activity can still be present. In other situations, where it is desirable that all chemosensory receptor activity is by the introduced exogenous hybrid receptor, use of a knockout line is preferred. Methods for the construction of non-human transgenic animals, particularly transgenic mice, and the selection and preparation of recombinant constructs for generating transformed cells are well known in the art.

[0226] Construction of a “knockout” cell and animal is based on the premise that the level of expression of a particular gene in a mammalian cell can be decreased or completely abrogated by introducing into the genome a new DNA sequence that serves to interrupt some portion of the DNA sequence of the gene to be suppressed. Also, “gene trap insertion” can be used to disrupt a host gene, and mouse embryonic stem (ES) cells can be used to produce knockout transgenic animals (see, e.g., Holzschu, Transgenic Res 6:97-106 (1997)). The insertion of the exogenous is typically by homologous recombination between complementary nucleic acid sequences. The exogenous sequence is some portion of the target gene to be modified, such as exonic, intronic or transcriptional regulatory sequences, or any genomic sequence which is able to affect the level of the target gene's expression; or a combination thereof. Gene targeting via homologous recombination in pluripotential embryonic stem cells allows one to modify precisely the genomic sequence of interest. Any technique can be used to create, screen for, propagate, a knockout animal, e.g., see Bijvoet, Hum. Mol. Genet. 7:53-62 (1998); Moreadith, J. Mol. Med. 75:208-216 (1997); Tojo, Cytotechnology 19:161-165 (1995); Mudgett, Methods Mol. Biol. 48:167-184 (1995); Longo, Transgenic Res. 6:321-328 (1997); U.S. Pat. Nos. 5,616,491; 5,464,764; 5,631,153; 5,487,992; 5,627,059; 5,272,071; WO 91/09955; WO93/09222; WO 96/29411; WO 95/31560; WO 91/12650.

[0227] The nucleic acids of the invention can also be used as reagents to produce “knockout” human cells and their progeny. Likewise, the nucleic acids of the invention can also be used as reagents to produce “knock-ins” in mice. The human or rat T1R gene sequences can replace the orthologous T1R in the mouse genome. In this way, a mouse expressing a human or rat T1R is produced. This mouse can then be used to analyze the function of human or rat T1Rs, and to identify ligands for such T1Rs.

[0228] D. Modulators

[0229] The compounds tested as modulators of a T1R family member can be any small chemical compound, or a biological entity, such as a protein, sugar, nucleic acid or lipid. Alternatively, modulators can be genetically altered versions of a T1R gene. Typically, test compounds will be small chemical molecules and peptides. Essentially any chemical compound can be used as a potential modulator or ligand in the assays of the invention, although most often compounds can be dissolved in aqueous or organic (especially DMSO-based) solutions are used. The assays are designed to screen large chemical libraries by automating the assay steps and providing compounds from any convenient source to assays, which are typically run in parallel (e.g., in microtiter formats on microtiter plates in robotic assays). It will be appreciated that there are many suppliers of chemical compounds, including Sigma (St. Louis, Mo.), Aldrich (St. Louis, Mo.), Sigma-Aldrich (St. Louis, Mo.), Fluka Chemika-Biochemica Analytika (Buchs, Switzerland) and the like.

[0230] In one preferred embodiment, high throughput screening methods involve providing a combinatorial chemical or peptide library containing a large number of potential therapeutic compounds (potential modulator or ligand compounds). Such “combinatorial chemical libraries” or “ligand libraries” are then screened in one or more assays, as described herein, to identify those library members (particular chemical species or subclasses) that display a desired characteristic activity. The compounds thus identified can serve as conventional “lead compounds” or can themselves be used as potential or actual therapeutics.

[0231] A combinatorial chemical library is a collection of diverse chemical compounds generated by either chemical synthesis or biological synthesis, by combining a number of chemical “building blocks” such as reagents. For example, a linear combinatorial chemical library such as a polypeptide library is formed by combining a set of chemical building blocks (amino acids) in every possible way for a given compound length (i.e., the number of amino acids in a polypeptide compound). Millions of chemical compounds can be synthesized through such combinatorial mixing of chemical building blocks.

[0232] Preparation and screening of combinatorial chemical libraries is well known to those of skill in the art. Such combinatorial chemical libraries include, but are not limited to, peptide libraries (see, e.g., U.S. Pat. No. 5,010,175, Furka, Int. J. Pept. Prot. Res., 37:487-493 (1991) and Houghton et al., Nature, 354:84-88 (1991)). Other chemistries for generating chemical diversity libraries can also be used. Such chemistries include, but are not limited to: peptoids (e.g., PCT Publication No. WO 91/19735), encoded peptides (e.g., PCT Publication WO 93/20242), random bio-oligomers (e.g., PCT Publication No. WO 92/00091), benzodiazepines (e.g., U.S. Pat. No. 5,288,514), diversomers such as hydantoins, benzodiazepines and dipeptides (Hobbs et al., Proc. Nat. Acad. Sci., 90:6909-6913 (1993)), vinylogous polypeptides (Hagihara et al., J. Amer. Chem. Soc., 114:6568 (1992)), nonpeptidal peptidomimetics with glucose scaffolding (Hirschmann et al., J. Amer. Chem. Soc., 114:9217-9218 (1992)), analogous organic syntheses of small compound libraries (Chen et al., J. Amer. Chem. Soc., 116:2661 (1994)), oligocarbamates (Cho et al., Science, 261:1303 (1993)), peptidyl phosphonates (Campbell et al., J. Org. Chem., 59:658 (1994)), nucleic acid libraries (Ausubel, Berger and Sambrook, all supra), peptide nucleic acid libraries (U.S. Pat. No. 5,539,083), antibody libraries (Vaughn et al., Nature Biotechnology, 14(3):309-314 (1996) and PCT/US96/10287), carbohydrate libraries (Liang et al., Science, 274:1520-1522 (1996) and U.S. Pat. No. 5,593,853), small organic molecule libraries (benzodiazepines, Baum, C&EN, Jan 18, page 33 (1993); thiazolidinones and metathiazanones, U.S. Pat. No. 5,549,974; pynrolidines, U.S. Pat. Nos. 5,525,735 and 5,519,134; morpholino compounds, U.S. Pat. No. 5,506,337; benzodiazepines, U.S. Pat. No. 5,288,514, and the like).

[0233] Devices for the preparation of combinatorial libraries are commercially available (see, e.g., 357 MPS, 390 MPS (Advanced Chem Tech, Louisville Ky.), Symphony (Rainin, Woburn, Mass.), 433A (Applied Biosystems, Foster City, Calif.), 9050 Plus (Millipore, Bedford, Mass.)). In addition, numerous combinatorial libraries are themselves commercially available (see, e.g., ComGenex, Princeton, N.J.; Tripos, Inc., St. Louis, Mo.; 3D Pharmaceuticals, Exton, Pa.; Martek Biosciences; Columbia, Md.; etc.).

[0234] In one aspect of the invention, the T1R modulators can be used in any food product, confectionery, pharmaceutical composition, or ingredient thereof to thereby modulate the taste of the product, composition, or ingredient in a desired manner. For instance, T1R modulators which enhance sweet taste sensation can be added to sweeten a product or composition, while T1R modulators which block undesirable taste sensations can be added to improve the taste of a product or composition.

[0235] E. Methods for Representing and Predicting the Perception of Taste

[0236] The invention also preferably provides methods for representing the perception of taste and/or for predicting the perception of taste in a mammal, including in a human. Preferably, such methods may be performed by using the receptors and genes encoding said T1R polypeptides disclosed herein.

[0237] Also contemplated as within the invention, is a method of screening one or more compounds for the presence of a taste detectable by a mammal, comprising: contacting said one or more compounds with the disclosed receptors, preferably wherein the mammal is a human. Also contemplated as within the invention, is a method for representing taste perception of a particular taste in a mammal, comprising the steps of: providing values Xi to Xn representative of the quantitative stimulation of each of n chemosensory receptors of said vertebrate, where n is greater than or equal to 2; and generating from said values a quantitative representation of taste perception. The chemosensory receptors may be a chemosensory receptor disclosed herein, the representation may constitutes a point or a volume in n-dimensional space, may constitutes a graph or a spectrum, and may constitutes a matrix of quantitative representations. Also, the providing step may comprise contacting a plurality of recombinantly-produced chemosensory receptors with a test composition and quantitatively measuring the interaction of said composition with said receptors.

[0238] Also contemplated as within the invention, is a method for predicting the taste perception in a mammal generated by one or more molecules or combinations of molecules yielding unknown taste perception in a mammal, comprising the steps of: providing values X₁ to X_(n) representative of the quantitative stimulation of each of n chemosensory receptors of said vertebrate, where n is greater than or equal to 2, for one or more molecules or combinations of molecules yielding known taste perception in a mammal; and generating from said values a quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding known taste perception in a mammal, providing values X₁ to X_(n) representative of the quantitative stimulation of each of n chemosensory receptors of said vertebrate, where n is greater than or equal to 2, for one or more molecules or combinations of molecules yielding unknown taste perception in a mammal; and generating from said values a quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding unknown taste perception in a mammal, and predicting the taste perception in a mammal generated by one or more molecules or combinations of molecules yielding unknown taste perception in a mammal by comparing the quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding unknown taste perception in a mammal to the quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding known taste perception in a mammal. The chemosensory receptors used in this method may include a chemosensory receptor disclosed herein.

[0239] In another embodiment, novel molecules or combinations of molecules are generated which elicit a predetermined taste perception in a mammal by determining a value of taste perception in a mammal for a known molecule or combinations of molecules as described above; determining a value of taste perception in a mammal for one or more unknown molecules or combinations of molecules as described above; comparing the value of taste perception in a mammal for one or more unknown compositions to the value of taste perception in a mammal for one or more known compositions; selecting a molecule or combination of molecules that elicits a predetermined taste perception in a mammal; and combining two or more unknown molecules or combinations of molecules to form a molecule or combination of molecules that elicits a predetermined taste perception in a mammal. The combining step yields a single molecule or a combination of molecules that elicits a predetermined taste perception in a mammal.

[0240] In another embodiment of the invention, there is provided a method for simulating a taste, comprising the steps of: for each of a plurality of cloned chemosensory receptors, preferably human receptors, ascertaining the extent to which the receptor interacts with the taste stimulus; and combining a plurality of compounds, each having a previously-ascertained interaction with one or more of the receptors, in amounts that together provide a receptor-stimulation profile that mimics the profile for the taste stimulus. Interaction of a taste stimulus with a chemosensory receptor can be determined using any of the binding or reporter assays described herein. The plurality of compounds may then be combined to form a mixture. If desired, one or more of the plurality of the compounds can be combined covalently. The combined compounds substantially stimulate at least 75%, 80%, or 90% of the receptors that are substantially stimulated by the taste stimulus.

[0241] In another preferred embodiment of the invention, a plurality of standard compounds are tested against a plurality of chemosensory receptors to ascertain the extent to which the receptors each interact with each standard compound, thereby generating a receptor stimulation profile for each standard compound. These receptor stimulation profiles may then be stored in a relational database on a data storage medium. The method may further comprise providing a desired receptor-stimulation profile for a taste; comparing the desired receptor stimulation profile to the relational database; and ascertaining one or more combinations of standard compounds that most closely match the desired receptor-stimulation profile. The method may further comprise combining standard compounds in one or more of the ascertained combinations to simulate the taste.

[0242] F. Kits

[0243] T1R genes and their homologs are useful tools for identifying chemosensory receptor cells, for forensics and paternity determinations, and for examining taste transduction. T1R family member-specific reagents that specifically hybridize to T1R nucleic acids, such as T1R probes and primers, and T1R specific reagents that specifically bind to a T1R polypeptide, e.g., T1R antibodies are used to examine taste cell expression and taste transduction regulation.

[0244] Nucleic acid assays for the presence of DNA and RNA for a T1R family member in a sample include numerous techniques are known to those skilled in the art, such as southern analysis, northern analysis, dot blots, RNase protection, S1 analysis, amplification techniques such as PCR, and in situ hybridization. In in situ hybridization, for example, the target nucleic acid is liberated from its cellular surroundings in such as to be available for hybridization within the cell while preserving the cellular morphology for subsequent interpretation and analysis. The following articles provide an overview of the art of in situ hybridization: Singer et al., Biotechniques, 4:230250 (1986); Haase et al., Methods in Virology, vol. VII, pp.189-226 (1984); and Nucleic Acid Hybridization: A Practical Approach (Names et al., eds. 1987). In addition, a T1R polypeptide can be detected with the various immunoassay techniques described above. The test sample is typically compared to both a positive control (e.g., a sample expressing a recombinant T1R polypeptide) and a negative control.

[0245] The present invention also provides for kits for screening for modulators of T1R family members. Such kits can be prepared from readily available materials and reagents. For example, such kits can comprise any one or more of the following materials: T1R nucleic acids or proteins, reaction tubes, and instructions for testing T1R activity. Optionally, the kit contains a biologically active T1R receptor. A wide variety of kits and components can be prepared according to the present invention, depending upon the intended user of the kit and the particular needs of the user.

EXAMPLES

[0246] In the protein sequences presented herein, the one-letter code X or Xaa refers to any of the twenty common amino acid residues. In the DNA sequences presented herein, the one letter codes N or n refers to any of the of the four common nucleotide bases, A, T, C, or G.

Example 1 hT1R3

[0247] The hT1R3 genomic DNA is provided below as SEQ ID NO 1 and SEQ ID NO 2 with predicted coding sequences (cds) shown in boldface. The break between the 5′ and 3′ contigs is shown as elipses (‘ . . . ’). The hT1R3 predicted cds are described in SEQ ID NO 3. Finally, a preferred, predicted hT1R3 amino acid sequence is provided as SEQ ID NO 4, using the one-letter code for the amino acids. hT1R3 genomic DNA-5′ contig (SEQ ID NO 1) AGCCTGGCAGTGGCCTCAGGCAGAGTCTGACGCGCA (SEQ ID NO: 1) CAAACTTTCAGGCCCAGGAAGCGAGGACACCACTGG GGCCCCAGGGTGTGGCAAGTGAGGATGGCAAGGGTT TTGCTAAACAAATCCTCTGCCCGCTCCCCGCCCCGG GCTCACTCCATGTGAGGCCCCAGTCGGGGCAGCCAC CTGCCGTGCCTGTTGGAAGTTGCCTCTGCCATGCTG GGCCCTGCTGTCCTGGGCCTCAGCCTCTGGGCTCTC CTGCACCCTGGGACGGGGGCCCCATTGTGCCTGTCA CAGCAACTTAGGATGAAGGGGGACTACGTGCTGGGG GGGCTGTTCCCCCTGGGCGAGGCCGAGGAGGCTGGC CTCCGCAGCCGGACACGGCCCAGCAGCCCTGTGTGC ACCAGGTACAGAGGTGGGACGGCCTGGGTCGGGGTC AGGGTGACCAGGTCTGGGGTGCTCCTGAGCTGGGGC CGAGGTGGCCATCTGCGGTTCTGTGTGGCCCCAGGT TCTCCTCAAACGGCCTGCTCTGGGCACTGGCCATGA AAATGGCCGTGGAGGAGATCAACAACAAGTCGGATC TGCTGCCCGGGCTGCGCCTGGGCTACGACCTCTTTG ATACGTGCTCGGAGCCTGTGGTGGCCATGAAGCCCA GCCTCATGTTCCTGGCCAAGGCAGGCAGCCGCGACA TCGCCGCCTACTGCAACTACACGCAGTACCAGCCCC GTGTGCTGGCTGTCATCGGGCCCCACTCGTCAGAGC TCGCCATGGTCACCGGCAAGTTCTTCAGCTTCTTCC TCATGCCCCAGTGGGGCGCCCCCCACCATCACCCAC CCCCAACCAACCCCTGCCCCGTGGGAGCCCCTTGTG TCAGGAGAATGC hT1R3 genomic DNA—3′ contig (SEQ ID NO 2) ..................TACATGCACCCCACCCAG (SEQ ID NO 2) CCCTGCCCTGGGAGCCCTGTGTCAGAAGATGCTCTT GGCCTTGCAGGTCAGCTACGGTGCTAGCATGGAGCT GCTGAGCGCCCGGGAGACCTTCCCCTCCTTCTTCCG CACCGTGCCCAGCGACCGTGTGCAGCTGACGGCCGC CGCGGAGCTGCTGCAGGAGTTCGGCTGGAACTGGGT GGCCGCCCTGGGCAGCGACGACGAGTACGGCCGGCA GGGCCTGAGCATCTTCTCGGCCCTGGCCGCGGCACG CGGCATCTGCATCGCGCACGAGGGCCTGGTGCCGCT GCCCCGTGCCGATGACTCGCGGCTGGGGAAGGTGCA GGACGTCCTGCACCAGGTGAACCAGAGCAGCGTGCA GGTGGTGCTGCTGTTCGCCTCCGTGCACGCCGCCCA CGCCCTCTTCAACTACAGCATCAGCAGCAGGCTCTC GCCCAAGGTGTGGGTGGCCAGCGAGGCCTGGCTGAC CTCTGACCTGGTCATGGGGCTGCCCGGCATGGCCCA GATGGGCACGGTGCTTGGCTTCCTCCAGAGGGGTGC CCAGCTGCACGAGTTCCCCCAGTACGTGAAGACGCA CCTGGCCCTGGCCACCGACCCGGCCTTCTGCTCTGC CCTGGGCGAGAGGGAGCAGGGTCTGGAGGAGGACGT GGTGGGCCAGCGCTGCCCGCAGTGTGACTGCATCAC GCTGCAGAACGTGAGCGCAGGGCTAAATCACCACCA GACGTTCTCTGTCTACGCAGCTGTGTATAGCGTGGC CCAGGCCCTGCACAACACTCTTCAGTGCAACGCCTC AGGCTGCCCCGCGCAGGACCCCGTGAAGCCCTGGCA GGTGAGCCCGGGAGATGGGGGTGTGCTGTCCTCTGC ATGTGCCCAGGCCACCAGGCACGGCCACCACGCCTG AGCTGGAGGTGGCTGGCGGCTCAGCCCCGTCCCCCG CCCGCAGCTCCTGGAGAACATGTACAACCTGACCTT CCACGTGGGCGGGCTGCCGCTGCGGTTCGACAGCAG CGGAAACGTGGACATGGAGTACGACCTGAAGCTGTG GGTGTGGCAGGGCTCAGTGCCCAGGCTCCACGACGT GGGCAGGTTCAACGGCAGCCTCAGGACAGAGCGCCT GAAGATCCGCTGGCACACGTCTGACAACCAGGTGAG GTGAGGGTGGGTGTGCCAGGCGTGCCCGTGGTAGCC CCCGCGGCAGGGCGCAGCCTGGGGGTGGGGGCCGTT CCAGTCTCCCGTGGGCATGCCCAGCCGAGCAGAGCC AGACCCCAGGCCTGTGCGCAGAAGCCCGTGTCCCGG TGCTCGCGGCAGTGCCAGGAGGGCCAGGTGCGCCGG GTCAAGGGGTTCCACTCCTGCTGCTACGACTGTGTG GACTGCGAGGCGGGCAGCTACCGGCAAAACCCAGGT GAGCCGCCTTCCCGGCAGGCGGGGGTGGGAACGCAG CAGGGGAGGGTCCTGCCAAGTCCTGACTCTGAGACC AGAGCCCACAGGGTACAAGACGAACACCCAGCGCCC TTCTCCTCTCTCACAGACGACATCGCCTGCACCTTT TGTGGCCAGGATGAGTGGTCCCCGGAGCGAAGCACA CGCTGCTTCCGCCGCAGGTCTCGGTTCCTGGCATGG GGCGAGCCGGCTGTGCTGCTGCTGCTCCTGCTGCTG AGCCTGGCGCTGGGCCTTGTGCTGGCTGCTTTGGGG CTGTTCGTTCACCATCGGGACAGCCCACTGGTTCAG GCCTCGGGGGGGCCCCTGGCCTGCTTTGGCCTGGTG TGCCTGGGCCTGGTCTGCCTCAGCGTCCTCCTGTTC CCTGGCCAGCCCAGCCCTGCCCGATGCCTGGCCCAG CAGCCCTTGTCCCACCTCCCGCTCACGGGCTGCCTG AGCACACTCTTCCTGCAGGCGGCCGAGATCTTCGTG GAGTCAGAACTGCCTCTGAGCTGGGCAGACCGGCTG AGTGGCTGCCTGCGGGGGCCCTGGGCCTGGCTGGTG GTGCTGCTGGCCATGCTGGTGGAGGTCGCACTGTGC ACCTGGTACCTGGTGGCCTTCCCGCCGGAGGTGGTG ACGGACTGGCACATGCTGCCCACGGAGGCGCTGGTG CACTGCCGCACACGCTCCTGGGTCAGCTTCGGCCTA GCGCACGCCACCAATGCCACGCTGGCCTTTCTCTGC TTCCTGGGCACTTTCCTGGTGCGGAGCCAGCCGGGC TGCTACAACCGTGCCCGTGGCCTCACCTTTGCCATG CTGGCCTACTTCATCACCTGGGTCTCCTTTGTGCCC CTCCTGGCCAATGTGCAGGTGGTCCTCAGGCCCGCC GTGCAGATGGGCGCCCTCCTGCTCTGTGTCCTGGGC ATCCTGGCTGCCTTCCACCTGCCCAGGTGTTACCTG CTCATGCGGCAGCCAGGGCTCAACACCCCCGAGTTC TTCCTGGGAGGGGGCCCTGGGGATGCCCAAGGCCAG AATGACGGGAACACAGGAAATCAGGGGAAACATGAG TGACCCAACCCTGTGATCTCAGCCCCGGTGAACCCA GACTTAGCTGCGATCCCCCCCAAGCCAGCAATGACC CGTGTCTCGCTACAGAGACCCTCCCGCTCTAGGTTC TGACCCCAGGTTGTCTCCTGACCCTGACCCCACAGT GAGCCCTAGGCCTGGAGCACGTGGACACCCCTGTGA CCATC hT1R3 full-length genomic DNA (SEQ ID NO 20) AGCCTGGCAGTGGCCTCAGGCAGAGTCTGACGCGCA (SEQ ID NO 20) CAAACTTTCAGGCCCAGGAAGCGAGGACACCACTGG GGCCCCAGGGTGTGGCAAGTGAGGATGGCAAGGGTT TTGCTAAACAAATCCTCTGCCCGCTCCCCGCCCCGG GCTCACTCCATGTGAGGCCCCAGTCGGGGCAGCCAC CTGCCGTGCCTGTTGGAAGTTGCCTCTGCCATGCTG GGCCCTGCTGTCCTGGGCCTCAGCCTCTGGGCTCTC CTGCACCCTGGGACGGGGGCCCCATTGTGCCTGTCA CAGCAACTTAGGATGAAGGGGGACTACGTGCTGGGG GGGCTGTTCCCCCTGGGCGAGGCCGAGGAGGCTGGC CTCCGCAGCCGGACACGGCCCAGCAGCCCTGTGTGC ACCAGGTACAGAGGTGGGACGGCCTGGGTCGGGGTC AGGGTGACCAGGTCTGGGGTGCTCCTGAGCTGGGGC CGAGGTGGCCATCTGCGGTTCTGTGTGGCCCCAGGT TCTCCTCAAACGGCCTGCTCTGGGCACTGGCCATGA AAATGGCCGTGGAGGAGATCAACAACAAGTCGGATC TGCTGCCCGGGCTGCGCCTGGGCTACGACCTCTTTG ATACGTGCTCGGAGCCTGTGGTGGCCATGAAGCCCA GCCTCATGTTCCTGGCCAAGGCAGGCAGCCGCGACA TCGCCGCCTACTGCAACTACACGCAGTACCAGCCCC GTGTGCTGGCTGTCATCGGGCCCCACTCGTCAGAGC TCGCCATGGTCACCGGCAAGTTCTTCAGCTTCTTCC TCATGCCCCAGTGGGGCGCCCCCCACCATCACCCAC CCCCAACCAACCCCTGCCCCGTGGGAGCCCCTTGTG TCAGGAGAATGCTACATGCACCCCACCCAGCCCTGC CCTGGGAGCCCTGTGTCAGAAGATGCTCTTGGCCTT GCAGGTCAGCTACGGTGCTAGCATGGAGCTGCTGAG CGCCCGGGAGACCTTCCCCTCCTTCTTCCGCACCGT GCCCAGCGACCGTGTGCAGCTGACGGCCGCCGCGGA GCTGCTGCAGGAGTTCGGCTGGAACTGGGTGGCCGC CCTGGGCAGCGACGACGAGTACGGCCGGCAGGGCCT GAGCATCTTCTCGGCCCTGGCCGCGGCACGCGGCAT CTGCATCGCGCACGAGGGCCTGGTGCCGCTGCCCCG TGCCGATGACTCGCGGCTGGGGAAGGTGCAGGACGT CCTGCACCAGGTGAACCAGAGCAGCGTGCAGGTGGT GCTGCTGTTCGCCTCCGTGCACGCCGCCCACGCCCT CTTCAACTACAGCATCAGCAGCAGGCTCTCGCCCAA GGTGTGGGTGGCCAGCGAGGCCTGGCTGACCTCTGA CCTGGTCATGGGGCTGCCCGGCATGGCCCAGATGGG CACGGTGCTTGGCTTCCTCCAGAGGGGTGCCCAGCT GCACGAGTTCCCCCAGTACGTGAAGACGCACCTGGC CCTGGCCACCGACCCGGCCTTCTGCTCTGCCCTGGG CGAGAGGGAGCAGGGTCTGGAGGAGGACGTGGTGGG CCAGCGCTGCCCGCAGTGTGACTGCATCACGCTGCA GAACGTGAGCGCAGGGCTAAATCACCACCAGACGTT CTCTGTCTACGCAGCTGTGTATAGCGTGGCCCAGGC CCTGCACAACACTCTTCAGTGCAACGCCTCAGGCTG CCCCGCGCAGGACCCCGTGAAGCCCTGGCAGGTGAG CCCGGGAGATGGGGGTGTGCTGTCCTCTGCATGTGC CCAGGCCACCAGGCACGGCCACCACGCCTGAGCTGG AGGTGGCTGGCGGCTCAGCCCCGTCCCCCGCCCGCA GCTCCTGGAGAACATGTACAACCTGACCTTCCACGT GGGCGGGCTGCCGCTGCGGTTCGACAGCAGCGGAAA CGTGGACATGGAGTACGACCTGAAGCTGTGGGTGTG GCAGGGCTCAGTGCCCAGGCTCCACGACGTGGGCAG GTTCAACGGCAGCCTCAGGACAGAGCGCCTGAAGAT CCGCTGGCACACGTCTGACAACCAGGTGAGGTGAGG GTGGGTGTGCCAGGCGTGCCCGTGGTAGCCCCCGCG GCAGGGCGCAGCCTGGGGGTGGGGGCCGTTCCAGTC TCCCGTGGGCATGCCCAGCCGAGCAGAGCCAGACCC CAGGCCTGTGCGCAGAAGCCCGTGTCCCGGTGCTCG CGGCAGTGCCAGGAGGGCCAGGTGCGCCGGGTCAAG GGGTTCCACTCCTGCTGCTACGACTGTGTGGACTGC GAGGCGGGCAGCTACCGGCAAAACCCAGGTGAGCCG CCTTCCCGGCAGGCGGGGGTGGGAACGCAGCAGGGG AGGGTCCTGCCAAGTCCTGACTCTGAGACCAGAGCC CACAGGGTACAAGACGAACACCCAGCGCCCTTCTCC TCTCTCACAGACGACATCGCCTGCACCTTTTGTGGC CAGGATGAGTGGTCCCCGGAGCGAAGCACACGCTGC TTCCGCCGCAGGTCTCGGTTCCTGGCATGGGGCGAG CCGGCTGTGCTGCTGCTGCTCCTGCTGCTGAGCCTG GCGCTGGGCCTTGTGCTGGCTGCTTTGGGGCTGTTC GTTCACCATCGGGACAGCCCACTGGTTCAGGCCTCG GGGGGGCCCCTGGCCTGCTTTGGCCTGGTGTGCCTG GGCCTGGTCTGCCTCAGCGTCCTCCTGTTCCCTGGC CAGCCCAGCCCTGCCCGATGCCTGGCCCAGCAGCCC TTGTCCCACCTCCCGCTCACGGGCTGCCTGAGCACA CTCTTCCTGCAGGCGGCCGAGATCTTCGTGGAGTCA GAACTGCCTCTGAGCTGGGCAGACCGGCTGAGTGGC TGCCTGCGGGGGCCCTGGGCCTGGCTGGTGGTGCTG CTGGCCATGCTGGTGGAGGTCGCACTGTGCACCTGG TACCTGGTGGCCTTCCCGCCGGAGGTGGTGACGGAC TGGCACATGCTGCCCACGGAGGCGCTGGTGCACTGC CGCACACGCTCCTGGGTCAGCTTCGGCCTAGCGCAC GCCACCAATGCCACGCTGGCCTTTCTCTGCTTCCTG GGCACTTTCCTGGTGCGGAGCCAGCCGGGCTGCTAC AACCGTGCCCGTGGCCTCACCTTTGCCATGCTGGCC TACTTCATCACCTGGGTCTCCTTTGTGCCCCTCCTG GCCAATGTGCAGGTGGTCCTCAGGCCCGCCGTGCAG ATGGGCGCCCTCCTGCTCTGTGTCCTGGGCATCCTG GCTGCCTTCCACCTGCCCAGGTGTTACCTGCTCATG CGGCAGCCAGGGCTCAACACCCCCGAGTTCTTCCTG GGAGGGGGCCCTGGGGATGCCCAAGGCCAGAATGAC GGGAACACAGGAAATCAGGGGAAACATGAGTGACCC AACCCTGTGATCTCAGCCCCGGTGAACCCAGACTTA GCTGCGATCCCCCCCAAGCCAGCAATGACCCGTGTC TCGCTACAGAGACCCTCCCGCTCTAGGTTCTGACCC CAGGTTGTCTCCTGACCCTGACCCCACAGTGAGCCC TAGGCCTGGAGCACGTGGACACCCCTGTGACCATC hT1R3 predicted cds (SEQ ID NO 3) ATGCTGGGCCCTGCTGTCCTGGGCCTCAGCCTCTGG (SEQ ID NO 3) GCTCTCCTGCACCCTGGGACGGGGGCCCCATTGTGC CTGTCACAGCAACTTAGGATGAAGGGGGACTACGTG CTGGGGGGGCTGTTCCCCCTGGGCGAGGCCGAGGAG GCTGGCCTCCGCAGCCGGACACGGCCCAGCAGCCCT GTGTGCACCAGGTTCTCCTCAAACGGCCTGCTCTGG GCACTGGCCATGAAAATGGCCGTGGAGGAGATCAAC AACAAGTCGGATCTGCTGCCCGGGCTGCGCCTGGGC TACGACCTCTTTGATACGTGCTCGGAGCCTGTGGTG GCCATGAAGCCCAGCCTCATGTTCCTGGCCAAGGCA GGCAGCCGCGACATCGCCGCCTACTGCAACTACACG CAGTACCAGCCCCGTGTGCTGGCTGTCATCGGGCCC CACTCGTCAGAGCTCGCCATGGTCACCGGCAAGTTC TTCAGCTTCTTCCTCATGCCCCAGGTCAGCTACGGT GCTAGCATGGAGCTGCTGAGCGCCCGGGAGACCTTC CCCTCCTTCTTCCGCACCGTGCCCAGCGACCGTGTG CAGCTGACGGCCGCCGCGGAGCTGCTGCAGGAGTTC GGCTGGAACTGGGTGGCCGCCCTGGGCAGCGACGAC GAGTACGGCCGGCAGGGCCTGAGCATCTTCTCGGCC CTGGCCGCGGCACGCGGCATCTGCATCGCGCACGAG GGCCTGGTGCCGCTGCCCCGTGCCGATGACTCGCGG CTGGGGAAGGTGCAGGACGTCCTGCACCAGGTGAAC CAGAGCAGCGTGCAGGTGGTGCTGCTGTTCGCCTCC GTGCACGCCGCCCACGCCCTCTTCAACTACAGCATC AGCAGCAGGCTCTCGCCCAAGGTGTGGGTGGCCAGC GAGGCCTGGCTGACCTCTGACCTGGTCATGGGGCTG CCCGGCATGGCCCAGATGGGCACGGTGCTTGGCTTC CTCCAGAGGGGTGCCCAGCTGCACGAGTTCCCCCAG TACGTGAAGACGCACCTGGCCCTGGCCACCGACCCG GCCTTCTGCTCTGCCCTGGGCGAGAGGGAGCAGGGT CTGGAGGAGGACGTGGTGGGCCAGCGCTGCCCGCAG TGTGACTGCATCACGCTGCAGAACGTGAGCGCAGGG CTAAATCACCACCAGACGTTCTCTGTCTACGCAGCT GTGTATAGCGTGGCCCAGGCCCTGCACAACACTCTT CAGTGCAACGCCTCAGGCTGCCCCGCGCAGGACCCC GTGAAGCCCTGGCAGCTCCTGGAGAACATGTACAAC CTGACCTTCCACGTGGGCGGGCTGCCGCTGCGGTTC GACAGCAGCGGAAACGTGGACATGGAGTACGACCTG AAGCTGTGGGTGTGGCAGGGCTCAGTGCCCAGGCTC CACGACGTGGGCAGGTTCAACGGCAGCCTCAGGACA GAGCGCCTGAAGATCCGCTGGCACACGTCTGACAAC CAGAAGCCCGTGTCCCGGTGCTCGCGGCAGTGCCAG GAGGGCCAGGTGCGCCGGGTCAAGGGGTTCCACTCC TGCTGCTACGACTGTGTGGACTGCGAGGCGGGCAGC TACCGGCAAAACCCAGACGACATCGCCTGCACCTTT TGTGGCCAGGATGAGTGGTCCCCGGAGCGAAGCACA CGCTGCTTCCGCCGCAGGTCTCGGTTCCTGGCATGG GGCGAGCCGGCTGTGCTGCTGCTGCTCCTGCTGCTG AGCCTGGCGCTGGGCCTTGTGCTGGCTGCTTTGGGG CTGTTCGTTCACCATCGGGACAGCCCACTGGTTCAG GCCTCGGGGGGGCCCCTGGCCTGCTTTGGCCTGGTG TGCCTGGGCCTGGTCTGCCTCAGCGTCCTCCTGTTC CCTGGCCAGCCCAGCCCTGCCCGATGCCTGGCCCAG CAGCCCTTGTCCCACCTCCCGCTCACGGGCTGCCTG AGCACACTCTTCCTGCAGGCGGCCGAGATCTTCGTG GAGTCAGAACTGCCTCTGAGCTGGGCAGACCGGCTG AGTGGCTGCCTGCGGGGGCCCTGGGCCTGGCTGGTG GTGCTGCTGGCCATGCTGGTGGAGGTCGCACTGTGC ACCTGGTACCTGGTGGCCTTCCCGCCGGAGGTGGTG ACGGACTGGCACATGCTGCCCACGGAGGCGCTGGTG CACTGCCGCACACGCTCCTGGGTCAGCTTCGGCCTA GCGCACGCCACCAATGCCACGCTGGCCTTTCTCTGC TTCCTGGGCACTTTCCTGGTGCGGAGCCAGCCGGGC TGCTACAACCGTGCCCGTGGCCTCACCTTTGCCATG CTGGCCTACTTCATCACCTGGGTCTCCTTTGTGCCC CTCCTGGCCAATGTGCAGGTGGTCCTCAGGCCCGCC GTGCAGATGGGCGCCCTCCTGCTCTGTGTCCTGGGC ATCCTGGCTGCCTTCCACCTGCCCAGGTGTTACCTG CTCATGCGGCAGCCAGGGCTCAACACCCCCGAGTTC TTCCTGGGAGGGGGCCCTGGGGATGCCCAAGGCCAG AATGACGGGAACACAGGAAATCAGGGGAAACATGAG TGA hT1R3 conceptual translation (SEQ ID NO 4) MLGPAVLGLSLWALLHPGTGAPLCLSQQLRMKGDYV (SEQ ID NO 4) LGGLFPLGEAEEAGLRSRTRPSSPVCTRFSSNGLLW ALAMKMAVEEINNKSDLLPGLRLGYDLFDTCSEPVV AMKPSLMFLAKAGSRDIAAYCNYTQYQPRVLAVIGP HSSELAMVTGKFFSFFLMPQVSYGASMELLSARETF PSFFRTVPSDRVQLTAAAELLQEFGWNWVAALGSDD EYGRQGLSIFSALAAARGICIAHEGLVPLPRADDSR LGKVQDVLHQVNQSSVQVVLLFASVHAAHALFNYSI SSRLSPKVWVASEAWLTSDLVMGLPGMAQMGTVLGF LQRGAQLHEFPQYVKTHLALATDPAFCSALGEREQG LEEDWGQRCPQCDCITLQNVSAGLNHHQTFSVYAAV YSVAQALHNTLQCNASGCPAQDPVKPWQLLENMYNL TFHVGGLPLRFDSSGNVDMEYDLKLWVWQGSVPRLH DVGRFNGSLRTERLKIRWHTSDNQKPVSRCSRQCQE GQVRRVKGFHSCCYDCVDCEAGSYRQNPDDIACTFC GQDEWSPERSTRCFRRRSRFLAWGEPAVLLLLLLLS LALGLVLAALGLFVHHRDSPLVQASGGPLACFGLVC LGLVCLSVLLFPGQPSPARCLAQQPLSHLPLTGCLS TLFLQAAEIFVESELPLSWADRLSGCLRGPWAWLWL LAMLVEVALCTWYLVAFPPEVVTDWHMLPTEALVHC RTRSWVSFGLAHATNATLAFLCFLGTFLVRSQPGCY NRARGLTFAMLAYFITWVSFVPLLANVQWLRPAVQM GALLLCVLGILAAFHLPRCYLLMRQPGLNTPEFFLG GGPGDAQGQNDGNTGNQGKHE

Example 2 rT1R3 and mT1R3

[0248] Segments of the rat and mouse T1R3 genes were isolated by PCR amplification from genomic DNA using degenerate primers based on the human T1R3 sequence. The degenerate primers SAP077 (5′-CGNTTYYTNGCNTGGGGNGARCC-3′; SEQ ID NO 5) and SAP079 (5′-CGNGCNCGRTTRTARCANCCNGG-3′; SEQ ID NO 6) are complementary to human T1R3 residues RFLAWGEPA (corresponding to SEQ ID NO 7) and PGCYNRAR (corresponding to SEQ ID NO 8), respectively. The PCR products were cloned and sequenced. Plasmid SAV115 carries a cloned segment of the mouse T1R3 gene, and SAV118 carries a segment of the rat gene. These sequences, shown below, clearly represent the rodent counterparts of human T1R3, since the mouse segment is 74% identical to the corresponding segment of human T1R3, and the rat segment is 80% identical to the corresponding segment of human T1R3. The mouse and rat segments are 88% identical. No other database sequences are more than 40% identical to these T1R3 segments. SAV115 mouse T1R3 segment in sense orientation (sequence corresponding to degenerate primer removed) (SEQ ID NO 9) GTGCTGTCACTCCTCCTGCTGCTTTGCCTGGTGCTGGGTCTAGCACTGGCTG (SEQ ID NO 9) CTCTGGGGCTCTCTGTCCACCACTGGGACAGCCCTCTTGTCCAGGCCTCAGG CGGCTCACAGTTCTGCTTTGGCCTGATCTGCCTAGGCCTCTTCTGCCTCAGT GTCCTTCTGTTCCCAGGACGGCCAAGCTCTGCCAGCTGCCTTGCACAACAAC CAATGGCTCACCTCCCTCTCACAGGCTGCCTGAGCACACTCTTCCTGCAAGC AGCTGAGACCTTTGTGGAGTCTGAGCTGCCACTGAGCTGGGCAAACTGGCTA TGCAGCTACCTTCGGGACTCTGGCCTGCTAGTGGTACTGTTGGCCACTTTTG TGGAGGCAGCACTATGTGCCTGGTATTTGACCGCTTCACCAGAAGTGGTGAC AGACTGGTCAGTGCTGCCCACAGAGGTACTGGAGCACTGCCACGTGCGTTCC TGGGTCAACCTGGGCTTGGTGCACATCACCMTGCAATGGTAGCTTTTCTCTG CTTTCTGGGCACTTTCCTGGTACAAGACCAG mT1R3 segment, conceptual translation (SEQ ID NO 10) VLSLLLLLCLVLGLALAALGLSVHHWDSPLVQASGGSQFCFGLICLGLFCLS (SEQ ID NO 10) VLLFPGRPSSASCLAQQPMAHLPLTGCLSTLFLQAAETFVESELPLSWANWL CSYLRDSGLLWLLATFVEAALCAWYLTASPEVVTDWSVLPTEVLEHCHVRSW VNLGLVHITNAMVAFLCFLGTFLVQDQ SAV118 rat T1R3 segment in sense orientation (sequence corresponding to degenerate primer removed) (SEQ ID NO 11) GTGCTGTCACTTCTCCTGCTGCTTTGCCTGGTGCTGGGCCTGACACTGGCTG (SEQ ID NO 11) CCCTGGGGCTCTTTGTCCACTACTGGGACAGCCCTCTTGTTCAGGCCTCAGG TGGGTCACTGTTCTGCTTTGGCCTGATCTGCCTAGGCCTCTTCTGCCTCAGT GTCCTTCTGTTCCCAGGACGACCACGCTCTGCCAGCTGCCTTGCCCAACAAC CAATGGCTCACCTCCCTCTCACAGGCTGCCTGAGCACACTCTTCCTGCAAGC AGCCGAGATCTTTGTGGAGTCTGAGCTGCCACTGAGTTGGGCAAACTGGCTC TGCAGCTACCTTCGGGGCCCCTGGGCTTGGCTGGTGGTACTGCTGGCCACTC TTGTGGAGGCTGCACTATGTGCCTGGTACTTGATGGCTTTCCCTCCAGAGGT GGTGACAGATTGGCAGGTGCTGCCCACGGAGGTACTGGAACACTGCCGCATG CGTTCCTGGGTCAGCCTGGGCTTGGTGCACATCACCAATGCAGGGGTAGCTT TCCTCTGCTTTCTGGGCACTTTCCTGGTACAAAGCCAG rT1R3 segment, conceptual translation (SEQ ID NO 12) VLSLLLLLCLVLGLTLAALGLFVHYWDSPLVQASGGSLFCFGLICLGLFCLS (SEQ ID NO 12) VLLFPGRPRSASCLAQQPMAHLPLTGCLSTLFLQAAEIFVESELPLSWANWL CSYLRGPWAWLWLLATLVEAALCAWYLMAFPPEWTDWQVLPTEVLEHCRMRS WVSLGLVHITNAGVAFLCFLGTFLVQSQ

Example 3 Cloning of rT1R3

[0249] The mT1R3 and rT1R3 fragments identified above as SEQ ID NOs 9 and 11 were used to screen a rat taste tissue-derived cDNA library. One positive clone was sequenced and found to contain the full-length rT1R3 sequence presented below as SEQ ID NO 13. Sequence comparison to the mT1R3 and rT1R3 partial sequences and to the full-length hT1R3 sequence established that this cDNA represents the rat counterpart to hT1R3. For example, the pairwise amino acid identity between rT1R3 and hT1R3 is approximately 72%, whereas the most related annotated sequence in public DNA sequence data banks is only approximately 33% identical to rT1R3. rT1R3 predicted cds (SEQ. ID NO. 13) ATGCCGGGTTTGGCTATCTTGGGCCTCAGTCTGGCTGCTTTCCTGGAGCTTG (SEQ ID NO 13) GGATGGGGTCCTCTTTGTGTCTGTCACAGCAATTCAAGGCACAAGGGGACTA TATATTGGGTGGACTATTTCCCCTGGGCACAACTGAGGAGGCCACTCTCAAC CAGAGAACACAGCCCAACGGCATCCTATGTACCAGGTTCTCGCCCCTTGGTT TGTTCCTGGCCATGGCTATGAAGATGGCTGTAGAGGAGATCAACAATGGATC TGCCTTGCTCCCTGGGCTGCGACTGGGCTATGACCTGTTTGACACATGCTCA GAGCCAGTGGTCACCATGAAGCCCAGCCTCATGTTCATGGCCAAGGTGGGAA GTCAAAGCATTGCTGCCTACTGCAACTACACACAGTACCAACCCCGTGTGCT GGCTGTCATTGGTCCCCACTCATCAGAGCTTGCCCTCATTACAGGCAAGTTC TTCAGCTTCTTCCTCATGCCACAGGTCAGCTATAGTGCCAGCATGGATCGGC TAAGTGACCGGGAAACATTTCCATCCTTCTTCCGCACAGTGCCCAGTGACCG GGTGCAGCTGCAGGCCGTTGTGACACTGTTGCAGAATTTCAGCTGGAACTGG GTGGCTGCCTTAGGTAGTGATGATGACTATGGCCGGGAAGGTCTGAGCATCT TTTCTGGTCTGGCCAACTCACGAGGTATCTGCATTGCACACGAGGGCCTGGT GCCACAACATGACACTAGTGGCCAACAATTGGGCAAGGTGGTGGATGTGCTA CGCCAAGTGAACCAAAGCAAAGTACAGGTGGTGGTGCTGTTTGCATCTGCCC GTGCTGTCTACTCCCTTTTTAGCTACAGCATCCTTCATGACCTCTCACCCAA GGTATGGGTGGCCAGTGAGTCCTGGCTGACCTCTGACCTGGTCATGACACTT CCCAATATTGCCCGTGTGGGCACTGTTCTTGGGTTTCTGCAGCGCGGTGCCC TACTGCCTGAATTTTCCCATTATGTGGAGACTCGCCTTGCCCTAGCTGCTGA CCCAACATTCTGTGCCTCCCTGAAAGCTGAGTTGGATCTGGAGGAGCGCGTG ATGGGGCCACGCTGTTCACAATGTGACTACATCATGCTACAGAACCTGTCAT CTGGGCTGATGCAGAACCTATCAGCTGGGCAGTTGCACCACCAAATATTTGC AACCTATGCAGCTGTGTACAGTGTGGCTCAGGCCCTTCACAACACCCTGCAG TGCAATGTCTCACATTGCCACACATCAGAGCCTGTTCAACCCTGGCAGCTCC TGGAGAACATGTACAATATGAGTTTCCGTGCTCGAGACTTGACACTGCAGTT TGATGCCAAAGGGAGTGTAGACATGGAATATGACCTGAAGATGTGGGTGTGG CAGAGCCCTACACCTGTACTACATACTGTAGGCACCTTCAACGGCACCCTTC AGCTGCAGCACTCGAAAATGTATTGGCCAGGCAACCAGGTGCCAGTCTCCCA GTGCTCCCGGCAGTGCAAAGATGGCCAGGTGCGCAGAGTAAAGGGCTTTCAT TCCTGCTGCTATGACTGTGTGGACTGCAAGGCAGGGAGCTACCGGAAGCATC CAGATGACTTCACCTGTACTCCATGTGGCAAGGATCAGTGGTCCCCAGAAAA AAGCACAACCTGCTTACCTCGCAGGCCCAAGTTTCTGGCTTGGGGGGAGCCA GCTGTGCTGTCACTTCTCCTGCTGCTTTGCCTGGTGCTGGGCCTGACACTGG CTGCCCTGGGGCTCTTTGTCCACTACTGGGACAGCCCTCTTGTTCAGGCCTC AGGTGGGTCACTGTTCTGCTTTGGCCTGATCTGCCTAGGCCTCTTCTGCCTC AGTGTCCTTCTGTTCCCAGGACGACCACGCTCTGCCAGCTGCCTTGCCCAAC AACCAATGGCTCACCTCCCTCTCACAGGCTGCCTGAGCACACTCTTCCTGCA AGCAGCCGAGATCTTTGTGGAGTCTGAGCTGCCACTGAGTTGGGCAAACTGG CTCTGCAGCTACCTTCGGGGCCCCTGGGCTTGGCTGGTGGTACTGCTGGCCA CTCTTGTGGAGGCTGCACTATGTGCCTGGTACTTGATGGCTTTCCCTCCAGA GGTGGTGACAGATTGGCAGGTGCTGCCCACGGAGGTACTGGAACACTGCCGC ATGCGTTCCTGGGTCAGCCTGGGCTTGGTGCACATCACCAATGCAGTGTTAG CTTTCCTCTGCTTTCTGGGCACTTTCCTGGTACAGAGCCAGCCTGGTCGCTA TAACCGTGCCCGTGGCCTCACCTTCGCCATGCTAGCTTATTTCATCATCTGG GTCTCTTTTGTGCCCCTCCTGGCTAATGTGCAGGTGGCCTACCAGCCAGCTG TGCAGATGGGTGCTATCTTATTCTGTGCCCTGGGCATCCTGGCCACCTTCCA CCTGCCCAAATGCTATGTACTTCTGTGGCTGCCAGAGCTCAACACCCAGGAG TTCTTCCTGGGAAGGAGCCCCAAGGAAGCATCAGATGGGAATAGTGGTAGTA GTGAGGCAACTCGGGGACACAGTGAATGA rT1R3 conceDtual translation (SEQ. ID NO. 14) MPGLAILGLSLAAFLELGMGSSLCLSQQFKAQGDYILGGLFPLGTTEEATLN (SEQ ID NO 14) QRTQPNGILCTRFSPLGLFLAMAMKMAVEEINNGSALLPGLRLGYDLFDTCS EPVVTMKPSLMFMAKVGSQSIAAYCNYTQYQPRVLAVIGPHSSELALITGKF FSFFLMPQVSYSASMDRLSDRETEPSFFRTVPSDRVQLQAVVTLLQNFSWNW VAALGSDDDYGREGLSIFSGLANSRGICIAHEGLVPQHDTSGQQLGKVVDVL RQVNQSKVQVVVLFASARAVYSLFSYSILHDLSPKVWVASESWLTSDLVMTL PNIARVGTVLGFLQRGALLPEFSHYVETRLALAADPTFCASLKAELDLEERV MGPRCSQCDYIMLQNLSSGLMQNLSAGQLHHQIFATYAAVYSVAQALHNTLQ CNVSHCHTSEPVQPWQLLENMYNMSFRARDLTLQFDAKGSVDMEYDLKMWVW QSPTPVLHTVGTFNGTLQLQHSKMYWPGNQVPVSQCSRQCKDGQVRRVKGFH SCCYDCVDCKAGSYRKHPDDFTCTPCGKDQWSPEKSTTCLPRRPKFLAWGEP AVLSLLLLLCLVLGLTLAALGLFVHYWDSPLVQASGGSLFCFGLICLGLFCL SVLLFPGRPRSASCLAQQPMAHLPLTGCLSTLFLQAAEIFVESELPLSWANW LCSYLRGPWAWLWLLATLVEAALCAWYLMAFPPEWTDWQVLPTEVLEHCRMR SWVSLGLVHITNAVLAFLCFLGTFLVQSQPGRYNRARGLTFAMLAYFIIWVS FVPLLANVQVAYQPAVQMGAILFCALGILATFHLPKCYVLLWLPELNTQEFF LGRSPKEASDGNSGSSEATRGHSE

Example 4 Expression of mT1R3

[0250] The above described mouse T1R3 fragment contained in SAV115 was PCR amplified using M13 forward and M13 reverse primers and then gel purified. The T1R3 DNA template was placed into an in vitro transcription labeling reaction where Digoxigenin labeled UTP was incorporated into an antisense cRNA probe. This probe was hybridized to adult mouse taste tissue containing cicumvallate papillae. The T1R3 in situ hybridization and detection were performed following the protocol of Schaeren-Wiemers et al., Histochemistry, 100:431-400 (1993). Briefly, fresh frozen mouse tongue was sectioned at 14 μm and prepared for hybridization. 200 ng/mL of the antisense Digoxigenin T1R3 probe was hybridized for 14 hours at 72° C. Posthybridization consisted of a 0.2×SSC wash at 72° C. Digoxigenin detection was accomplished by incubation with 1:5000 dilution of anti-DIG Alkaline Phosphatase antibody followed by a 12-hour reaction of the phosphatase in NBT/BCIP.

Example 5 hT1R1

[0251] The human ortholog (Database accession no. AL159177) of a rat taste receptor, designated rT1R1, is provided below as SEQ ID NO 15. Predicted cds are indicated in bold and some intronic sequence intervals are denoted as runs of N. The nucleotide and conceptually-translated hT1R1 sequences are also described herein as SEQ ID NO 16 and 17, respectively hT1R1 genomic DNA (SEQ ID NO 15) GAGAATCTCGCGAGATCCCGTCGGTCCGCCCCGCTGCCCTCCCAGCTGCCGA (SEQ ID NO 15) AAAGAGGGGCCTCCGAGCCGCCGGCGCCCTCTGCCGGCAACCTCCGGAAGCA CACTAGGAGGTTCCAGCCGATCTGGTCGAGGGGCTCCACGGAGGACTCCATT TACGTTACGCAAATTCCCTACCCCAGCCGGCCGGAGAGAGAAAGCCAGAAAC CTCGCGACCAGCCATGGGCCACCTCTCCGGAAAAACACCGGGATATTTTTTT TCTCCTGCAGAAAAAGCTTTAGGATTGGCAGTTTAAACAAAACATGTCTATT TGCATACCTTCGGTTTGCATGCATTTGTTTCGAAGTGAGCAACCCTGGGTAA CAAGGCGAAAGTATATGACAATTTGCTCAGAATCTTAATGTCAGAAAACTGG AGACTGGGGCAGGGGGGTGTCGACTCAAAGCTGTGTCTCATTTAGTAAACTG AGGCCCAGGTAAAAAGTTCTGAAACCTCGCAACACCCGGAGAAATTGTGTTC CAGCCTCCCACCTCGCCCCAAAATGCCAGAGCTCCTTTTCTAAGCCAGGTGA AGTCACAGAGCGTGGACAGAACCCACAACCGTCCAGAGGAAGGGTCACTGGG TGCCACCTGGTTTGCATCTGTGCCTTCGTCCTGCCCAGTTCCTGAGTGGGAC CGCAGGCCCGGAATGTCAAGGCAAACAGTCCTGCTTCAGCCACTGGGCTCCA GTCCCACCCCTTTTGGGGGCCTGAAGTTAGGAAGCATCCGGCAGCTGCCTTC TATTTAAGCAACTGGCCTCCTTAGAGGCCACTCCTTGGCCATGCCAGGCGCG GGCATCTGGCCAGCATGCTGCTCTGCACGGCTCGCCTGGTCGGCCTGCAGCT TCTCATTTCCTGCTGCTGGGCCTTTGCCTGCCATAGCACGGAGTCTTCTCCT GACTTCACCCTCCCCGGAGATTACCTCCTGGCAGGCCTGTTCCCTCTCCATT CTGGCTGTCTGCAGGTGAGGCACAGACCCGAGGTGACCCTGTGTGACAGGTG AGTGAGGGGCCAGCAGAGCCACACTTAGTGGGACCCCTGGCTATAGGGCCCC TCTGGCTGCCATCCTCCAAACAGGACCTTGCCTCTGCCTTTGCCCCTTGAAC TGTCCCCAGGCCTTGTTCATCAATCCACTTGCCACCTAAGTGCTGGCTAGAC CTTCCTAGACACTTCGGCCAGTTTCCAATTATTTCACCCTTGCTGTTAGAAT GTNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN AATTCCTTAAACTAAATTTCTCACTTTCTCTCTCTCTCTGGAAAACACTGAC TAATGTAGCAGGTTTCTCTGCTCCAGGACTTCAGGACCTTTTCGATGCTAAT AAGTTTCTCCATCAGGGCCAGCTTGTTCCTCCTACTGAGCTTGAGAGCCCTT GTTGAAGTTGTGGTTTGGGGGACTGGACCGATGACCTCAAAGGTTCCCTTTG CTCCCAAGCCTCAGAGTCTAGGAGGCCAGAGGGTCTCAGCAGGCCTTTGTCC TTCTCAGCTGTCTCTTACTGGCTTTCTCCACAGGTCTTGTAGCTTCAATGAG CATGGCTACCACCTCTTCCAGGCTATGCGGCTTGGGGTTGAGGAGATAAACA ACTCCACGGCCCTGCTGCCCAACATCACCCTGGGGTACCAGCTGTATGATGT GTGTTCTGACTCTGCCAATGTGTATGCCACGCTGAGAGTGCTCTCCCTGCCA GGGCAACACCACATAGAGCTCCAAGGAGACCTTCTCCACTATTCCCCTACGG TGCTGGCAGTGATTGGGCCTGACAGCACCAACCGTGCTGCCACCACAGCCGC CCTGCTGAGCCCTTTCCTGGTGCCCATGGTAAGCTGGAGCCTCAGACCTTTG CCCATCTCCCTTCAGGCAAGTCTGGGNNNNNNNNNNNNNNNNNNNNNNNNNN NNNNNNNNNNNNNNNNNNNNNNNNGCCACCATGCCCGGCTAATTTTTTTGTA TTTTTAGTAGAGACGGGGTTTCACCGTGTTAGCCAGGCTGGTCGCAAACTCC TAACCTCGTGATCCACCCACCTCGGCCTCCCAATGTGCTGGGATTACAGGTG TGAGCCACTGCACCCGGCCATAATGTATTAATATAATAAAATAATTATACAA CTCACCATAATGTAGAATCAGTGGGAGCCCTGAGCUGTTTTCCTACAACTAG ATGGTCCCATCTGGGGGTGATGGGAGACAGTGACAGATCATCAGACATTAGA TTCTCATAAGTAGCGTGCAACCCAGATCCCTCGCATGTGCAGTTCACAGTAG GGTTCAAGCTCCTACAAGAATCTGATGCTGCTGCTGATCTGACAGGAGGGGA GCAGCTGTAAATACAGATGAAGCTTCGCTTACTCACCAGCTGCTCACCTCCT CCTGTGAGGCCCGGTTCCTAACAGGCCACTGACCTAACTTCTGCCCTGACCT ACACATGCTTCTCTTCTTCCTTGCAAACTGCCTCCAGTGGAAGTCCCTGAAG GTCCCCAAACACACGGGACTATTTCACTCCTATGCAGGTTTTGTCTCCTTTG CTTGGAATGCATCCCCTCACCCCTTGTCCCCAGGCAGATTCCCACCCCTCCC CCAGAACCTGCCCCAGTGGAGCCTTCGCAGGTGATTTGTCAGTTTCACAGGC TGAGGGGTGCTCTCCTGGTCTCCCCGGCTCCCTGTATCCCCACACCCAGCAC AGGGCCAGGCACTGGGGGGGCCTTCAGTGGAGACTGAAATGGCTGAACGGGA CCTCCCATAGATTAGCTATGCGGCCAGCAGCGAGACGCTCAGCGTGAAGCGG CAGTATCCCTCTTTCCTGCGCACCATCCCCAATGACAAGTACCAGGTGGAGA CCATGGTGCTGCTGCTGCAGAAGTTCGGGTGGACCTGGATCTCTCTGGTTGG CAGCAGTGACGACTATGGGCAGCTAGGGGTGCAGGCACTGGAGAACCAGGCC ACTGGTCAGGGGATCTGCATTGCTTTCAAGGACATCATGCCCTTCTCTGCCC AGGTGGGCGATGAGAGGATGCAGTGCCTCATGCGCCACCTGGCCCAGGCCGG GGCCACCGTCGTGGTTGTTTTTTCCAGCCGGCAGTTGGCCAGGGTGTTTTTC GAGTCCGTGGTGCTGACCAACCTGACTGGCAAGGTGTGGGTCGCCTCAGAAG CCTGGGCCCTCTCCAGGCACATCACTGGGGTGCCCGGGATCCAGCGCATTGG GATGGTGCTGGGCGTGGCCATCCAGAAGAGGGCTGTCCCTGGCCTGAAGGCG TTTGAAGAAGCCTATGCCCGGGCAGACAAGAAGGCCCCTAGGCCTTGCCACA AGGGCTCCTGGTGCAGCAGCAATCAGCTCTGCAGAGAATGCCAAGCTTTCAT GGCACACACGATGCCCAAGCTCAAAGCCTTCTCCATGAGTTCTGCCTACAAC GCATACCGGGCTGTGTATGCGGTGGCCCATGGCCTCCACCAGCTCCTGGGCT GTGCCTCTGGAGCTTGTTCCAGGGGCCGAGTCTACCCCTGGCAGGTAAGAGA GCCCACCCCAGCACCTCCTGTCAGGGAGAACAGCCAATCCTGAGATGAGCAG AGTGGGCACTCTCCGGTCACTCTAAATGCCAAGGGGGATAAATGCCACTAAC TTGAGGTTTTTTGTTTTGTTTTGTTTTGTTTTTTGAGACAGTCTGGCTCTGT CACCCAGGCTGCAGTGTAGTGATGCGATCTCGGCTCTCTGCAACTTCCACCT CCTGGGTTCAAGTGATTCTCTTGCCTCGGCCTCCTGAGTAGCTGGGATTACA GGCACCCACCACCATGCCTGGATAATTTTTCTTTTCTTTTTTTTTTTTTTGA GATAGAGTCTCGCTCTGTTGCCCAGGCTGGAATGCAGTGGTGCGATCTTGGC TCACTGTGAGCTCCGCCTCCCAGGTTCACTCCATTCCCCTGCCTCAGCCTCC CAAGTAGGTGGGACTACGGGCGCCCGCCACCACGCCCAGCTAATTTTTTTTG TATTTTGAGTAGAGACGGGGTTTCACCATGTTAGCCAGGATGGTCTCAATCT CCTGACCTTGTCATCCGCCCACCTCGTCCTCCCAAAGTGCTGGGATTACAGG CGTGAGCCACCGCACCCGGCCTAATTTTTGTATTTTTAGTAGAGATGGGGTT TCACCATGTTGGCCAGGCTGGTCTCGAACTCCTGGCATCAAGTGATCCTCCT GCTTCGGCCTCCCAAAGTGCTGGGATTACAGGCATTAGCTCTCTTCTCTTAG ACAGATCTTTCTCTCTGATCCTTGCCTTCTCTCACCCACTGTGTCTTGGAAG TGTCAAGTGATAAGATCCAGGGCTAAAACTGTCTGTAAAGGAGTGTTTGTTA GAGGCCTCCTCTCAGGAGGTTGGTGGGGAAGATTGAGGGGCTTCCTAAGAAG GAAGGGACGAGACCTTCCTGATGGGCTGAAACCACCAGGACGGAAACCCAGG AAGGCCCCAGGCCCTTGCTTCTGGGACCATGTGGGTCTGTGCTGTCTGTGGT GGCTTCATGATACGCGTTTCTTTCAGCTTTTGGAGCAGATCCACAAGGTGCA TTTCCTTCTACACAAGGACACTGTGGCGTTTAATGACAACAGAGATCCCCTC AGTAGCTATAACATAATTGCCTGGGACTGGAATGGACCCAAGTGGACCTTCA CGGTCCTCGGTTCCTCCACATGGTCTCCAGTTCAGCTAAACATAAATGAGAC CAAAATCCAGTGGCACGGAAAGGACAACCAGGTAATGGGGATGTGGCTACTC ACCATGTAACTGGCTTATGGGCAACCTAGAGCCTGGGGGTGATGCTGACACA GTGTACAGGGAGCAGGAGGGGGGCCCCAGGGGTCCAGCTGCCACCACTCTAC CCATCCTGGCCAGGGAAGCAGGGAAGACACTCCGTAGGCGAGTGTGCAGATG CCCTGGGGCGGAAGTTCACACGACCAGGGGCCCTGCCCTGGGAGTGAGCCCT GAGGGCAGATGCACAGAGATTCTGTTTTCTGTTCCACATGTGAGCTGTCCTT TGACTTGGGCCCCTACGTGTGGCCCCTCTGGCTTCTTACAGGTGCCTAAGTC TGTGTGTTCCAGCGACTGTCTTGAAGGGCACCAGCGAGTGGTTACGGGTTTC CATCACTGCTGCTTTGAGTGTGTGCCCTGTGGGGCTGGGACCTTCCTCAACA AGAGTGGTGAGTGGGCAATGGAGCAGGCGAGCTACCCAGCACTCCCGGGGGC TGCACGGTGGAGGGAGGGCCTCCCTTGGGCCCCATGTGCCCTGCCCCAGAAC CAAGGCCCAGTCACTGGGCTGCCAGTTAGCTTCAGGTTGGAGGACACCTGCT ACCAGACAGAATTCTGATCAAGAGAATCAGCCACTGGGTGCGGTGGCTCATG CCTGTAATCCCAGCACTTTGGGAGGCTGAGGCGGGTGGATCACTTGAGGTCG GGAGTTCGAGACCAGCCTGGCCAACATGGTGAAACCCCATCTCTACCAAAAA TATAAAAAATTAGCTGGGTGTGGTGGCGCGTGCCTGTAATCCCAGCTACTCG GGAGGCTGAGGCAGGAGAATCACTTGAACCCAGGAGGCGGAGGTTGCAGTGA GCCAAGATGCATTCCAGCCTGGACCACAAAGCGAGAATTCGTCCCCCCAAAA AAAGAAAGGAGGCCGGGCGCGGTGGCTCACACCTGTAATCCCAGCACTTTGG GAGGCCGAGGTGGGTGGATCACCTGAGGTCAGGAGTTCGAGACCAGCCTGAC CAACATGGTGAAACCCCATCTCTACTAAAAATACAAAAAAAGTTAGCCGGGC GTTGTGGCGTGTGCCTGTAATTCCAGCTACTCGGGAGGCTGAGGCAGGAGAA TTGCTTGAACCCGGGAGGCGGAGGTTGCAGTGAGCCAAGATTGCACCATTGC ACTCCAGCCTGGGCGACAAGAGAAAAACTCTGTCTCAAAAAAAAAGAAAGAA AGAAAGAATTAGCCAACTGAAAGCCTTAGACTGAGGTGTGTCCTCTGTTAGA GAGCTGTCATCACAACTCCTACAAAAGCAGTCGTATCCTGAATTCAACCTCT TTCTCTAAATGAATATAGCTATTGTTCCCTTTGTGCCCTCTTGTCCTACTGT CCCCTTCTGTTGCCCATGCCAAAGACAGCTAGCTCCTTGAACAGCTTGGCCT GAATACAGATACTAGCGTGTCTGCAGCAGAGAAAAAAACAGCATTCCCCATC CAGAAATGCAAGGTCAAGAACAGAGAGCAAATTAGGTAGCTAAGGACTCAGG TCCTTAGTTGGTGTCCAGGGGCCACATTCTTTCCTTTCACCATCTCTGTAGG GACAGGAATACTTCCCTTCTGTCCTCAGAGGGTCAGGACTCAGAGAAACCAC AGAGCAGCAGCTCAGGAAAGTGGTTCATGGAAATGCTGGCAAGAGAGAGGGG TTACAATGCCCTCCCTTGGGAGCAGGCTGCTCCCATCAGATCGTAACCTCTC TGGTATGTGGGCAGAGCTACCAGGTTAAGGTCCTCCCTAGGGTTTGCAAAAC CCTCATGGGATCATGAGCCATACAGAACCGACCTGTGTGTCTCCAGAGTCTG TAATTAACACAGGCATTTTGAGGAAATGCGTGGCCTCAGGCCCCACTCCCGG CTACCCCCATCCCACTATGCCTAGTATAGTCTAGCTGCCCTGGTACAATTCT CCCAGTATCTTGCAGGCCCCTATTTCCTATTCCTACTCTGCTCATCTGGCTC TCAGGAACCTTCTTGGCCTTCCCTTTCAGACCTCTACAGATGCCAGCCTTGT GGGAAAGAAGAGTGGGCACCTGAGGGAAGCCAGACCTGCTTCCCGCGCACTG TGGTGTTTTTGGCTTTGCGTGAGCACACCTCTTGGGTGCTGCTGGCAGCTAA CACGCTGCTGCTGCTGCTGCTGCTTGGGACTGCTGGCCTGTTTGCCTGGCAC CTAGACACCCCTGTGGTGAGGTCAGCAGGGGGCCGCCTGTGCTTTCTTATGC TGGGCTCCCTGGCAGCAGGTAGTGGCAGCCTCTATGGCTTCTTTGGGGAACC CACAAGGCCTGCGTGCTTGCTACGCCAGGCCCTCTTTGCCCTTGGTTTCACC ATCTTCCTGTCCTGCCTGACAGTTCGCTCATTCCAACTAATCATCATCTTCA AGTTTTCCACCAAGGTACCTACATTCTACCACGCCTGGGTCCAAAACCACGG TGCTGGCCTGTTTGTGATGATCAGCTCAGCGGCCCAGCTGCTTATCTGTCTA ACTTGGCTGGTGGTGTGGACCCCACTGCCTGCTAGGGAATACCAGCGCTTCC CCCATCTGGTGATGCTTGAGTGCACAGAGACCAACTCCCTGGGCTTCATACT GGCCTTCCTCTACAATGGCCTCCTCTCCATCAGTGCCTTTGCCTGCAGCTAC CTGGGTAAGGACTTGCCAGAGAACTACAACGAGGCCAAATGTGTCACCTTCA GCCTGCTCTTCAACTTCGTGTCCTGGATCGCCTTCTTCACCACGGCCAGCGT CTACGACGGCAAGTACCTGCCTGCGGCCAACATGATGGCTGGGCTGAGCAGC CTGAGCAGCGGCTTCGGTGGGTATTTTCTGCCTAAGTGCTACGTGATCCTCT GCCGCCCAGACCTCAACAGCACAGAGCACTTCCAGGCCTCCATTCAGGACTA CACGAGGCGCTGCGGCTCCACCTGACCAGTGGGTCAGCAGGCACGGCTGGCA GCCTTCTCTGCCCTGAGGGTCGAAGGTCGAGCAGGCCGGGGGTGTCCGGGAG GTCTTTGGGCATCGCGGTCTGGGGTTGGGACGTGTAAGCGCCTGGGAGAGCC TAGACCAGGCTCCGGGCTGCCAATAAAGAAGTGAAATGCGTATCTGGTCTCC TGTCGTGGGAGAGTGTGAGGTGTAACGGATTCAAGTCTGAACCCAGAGCCTG GAAAAGGCTGACCGCCCAGATTGACGTTGCTAGGCAACTCCGGAGGCGGGCC CAGCGCCAAAAGAACAGGGCGAGGCGTCGTCCCCGCATCCCATTGGCCGTTC TCTGCGGGGCCCCGCCCTCGGGGGCCGGAGCTAGAAGCTCTACGCTTCCGAG GCGCACCTCCTGGCCTGCACGCTTTGACGT hT1R1 Predicted cds (SEQ ID NO 16) ATGCTGCTCTGCACGGCTCGCCTGGTCGGCCTGCAGCTTCTCATTTCCTGCT (SEQ ID NO 16) GCTGGGCCTTTGCCTGCCATAGCACGGAGTCTTCTCCTGACTTCACCCTCCC CGGAGATTACCTCCTGGCAGGCCTGTTCCCTCTCCATTCTGGCTGTCTGCAG GTGAGGCACAGACCCGAGGTGACCCTGTGTGACAGGTCTTGTAGCTTCAATG AGCATGGCTACCACCTCTTCCAGGCTATGCGGCTTGGGGTTGAGGAGATAAA CAACTCCACGGCCCTGCTGCCCAACATCACCCTGGGGTACCAGCTGTATGAT GTGTGTTCTGACTCTGCCAATGTGTATGCCACGCTGAGAGTGCTCTCCCTGC CAGGGCAACACCACATAGAGCTCCAAGGAGACCTTCTCCACTATTCCCCTAC GGTGCTGGCAGTGATTGGGCCTGACAGCACCAACCGTGCTGCCACCACAGCC GCCCTGCTGAGCCCTTTCCTGGTGCCCATGATTAGCTATGCGGCCAGCAGCG AGACGCTCAGCGTGAAGCGGCAGTATCCCTCTTTCCTGCGCACCATCCCCAA TGACAAGTACCAGGTGGAGACCATGGTGCTGCTGCTGCAGAAGTTCGGGTGG ACCTGGATCTCTCTGGTTGGCAGCAGTGACGACTATGGGCAGCTAGGGGTGC AGGCACTGGAGAACCAGGCCACTGGTCAGGGGATCTGCATTGCTTTCAAGGA CATCATGCCCTTCTCTGCCCAGGTGGGCGATGAGAGGATGCAGTGCCTCATG CGCCACCTGGCCCAGGCCGGGGCCACCGTCGTGGTTGTTTTTTCCAGCCGGC AGTTGGCCAGGGTGTTTTTCGAGTCCGTGGTGCTGACCAACCTGACTGGCAA GGTGTGGGTCGCCTCAGAAGCCTGGGCCCTCTCCAGGCACATCACTGGGGTG CCCGGGATCCAGCGCATTGGGATGGTGCTGGGCGTGGCCATCCAGAAGAGGG CTGTCCCTGGCCTGAAGGCGTTTGAAGAAGCCTATGCCCGGGCAGACAAGAA GGCCCCTAGGCCTTGCCACAAGGGCTCCTGGTGCAGCAGCAATCAGCTCTGC AGAGAATGCCAAGCTTTCATGGCACACACGATGCCCAAGCTCAAAGCCTTCT CCATGAGTTCTGCCTACAACGCATACCGGGCTGTGTATGCGGTGGCCCATGG CCTCCACCAGCTCCTGGGCTGTGCCTCTGGAGCTTGTTCCAGGGGCCGAGTC TACCCCTGGCAGCTTTTGGAGCAGATCCACAAGGTGCATTTCCTTCTACACA AGGACACTGTGGCGTTTAATGACAACAGAGATCCCCTCAGTAGCTATAACAT AATTGCCTGGGACTGGAATGGACCCAAGTGGACCTTCACGGTCCTCGGTTCC TCCACATGGTCTCCAGTTCAGCTAAACATAAATGAGACCAAAATCCAGTGGC ACGGAAAGGACAACCAGGTGCCTAAGTCTGTGTGTTCCAGCGACTGTCTTGA AGGGCACCAGCGAGTGGTTACGGGTTTCCATCACTGCTGCTTTGAGTGTGTG CCCTGTGGGGCTGGGACCTTCCTCAACAAGAGTGACCTCTACAGATGCCAGC CTTGTGGGAAAGAAGAGTGGGCACCTGAGGGAAGCCAGACCTGCTTCCCGCG CACTGTGGTGTTTTTGGCTTTGCGTGAGCACACCTCTTGGGTGCTGCTGGCA GCTAACACGCTGCTGCTGCTGCTGCTGCTTGGGACTGCTGGCCTGTTTGCCT GGCACCTAGACACCCCTGTGGTGAGGTCAGCAGGGGGCCGCCTGTGCTTTCT TATGCTGGGCTCCCTGGCAGCAGGTAGTGGCAGCCTCTATGGCTTCTTTGGG GAACCCACAAGGCCTGCGTGCTTGCTACGCCAGGCCCTCTTTGCCCTTGGTT TCACCATCTTCCTGTCCTGCCTGACAGTTCGCTCATTCCAACTAATCATCAT CTTCAAGTTTTCCACCAAGGTACCTACATTCTACCACGCCTGGGTCCAAAAC CACGGTGCTGGCCTGTTTGTGATGATCAGCTCAGCGGCCCAGCTGCTTATCT GTCTAACTTGGCTGGTGGTGTGGACCCCACTGCCTGCTAGGGAATACCAGCG CTTCCCCCATCTGGTGATGCTTGAGTGCACAGAGACCAACTCCCTGGGCTTC ATACTGGCCTTCCTCTACAATGGCCTCCTCTCCATCAGTGCCTTTGCCTGCA GCTACCTGGGTAAGGACTTGCCAGAGAACTACAACGAGGCCAAATGTGTCAC CTTCAGCCTGCTCTTCAACTTCGTGTCCTGGATCGCCTTCTTCACCACGGCC AGCGTCTACGACGGCAAGTACCTGCCTGCGGCCAACATGATGGCTGGGCTGA GCAGCCTGAGCAGCGGCTTCGGTGGGTATTTTCTGCCTAAGTGCTACGTGAT CCTCTGCCGCCCAGACCTCAACAGCACAGAGCACTTCCAGGCCTCCATTCAG GACTACACGAGGCGCTGCGGCTCCACCTGA hT1R1 conceptual translation (SEQ ID NO 17) MLLCTARLVGLQLLISCCWAFACHSTESSPDFTLPGDYLLAGLFPLHSGCLQ (SEQ ID NO 17) VRHRPEVTLCDRSCSFNEHGYHLFQAMRLGVEEINNSTALLPNITLGYQLYD VCSDSANVYATLRVLSLPGQHHIELQGDLLHYSPTVLAVIGPDSTNRAATTA ALLSPFLVPMISYAASSETLSVKRQYPSFLRTIPNDKYQVETMVLLLQKFGW TWISLVGSSDDYGQLGVQALENQATGQGICIAFKDIMPFSAQVGDERMQCLM RHLAQAGATVWVFSSRQLARVFFESWLTNLTGKVWVASEAWALSRHITGVPG IQRIGMVLGVAIQKRAVPGLKAFEEAYARADKKAPRPCHKGSWCSSNQLCRE CQAFMAHTMPKLKAFSMSSAYNAYRAVYAVAHGLHQLLGCASGACSRGRVYP WQLLEQIHKVHFLLHKDTVAFNDNRDPLSSYNIIAWDWNGPKWTFTVLGSST WSPVQLNINETKIQWHGKDNQVPKSVCSSDCLEGHQRWTGFHHCCFECVPCG AGTFLNKSDLYRCQPCGKEEWAPEGSQTCFPRTVVFLALREHTSWVLLAANT LLLLLLLGTAGLFAWHLDTPWRSAGGRLCFLMLGSLAAGSGSLYGFFGEPTR PACLLRQALFALGFTIFLSCLTVRSFQLIIIFKFSTKVPTFYHAWVQNHGAG LFVMISSAAQLLICLTWLVVWTPLPAREYQRFPHLVMLECTETNSLGFILAF LYNGLLSISAFACSYLGKDLPENYNEAKCVTFSLLFNFVSWIAFFTTASVYD GKYLPAANMMAGLSSLSSGFGGYFLPKCWILCRPDLNSTEHFQASIQDYTRR CGST

Example 6 hT1R2

[0252] The predicted cds of the human ortholog of a rat taste receptor, designated rT1R2, is provided below as SEQ ID NO 20. The conceptually-translated hT1R2 sequences is also described herein as SEQ ID NO 21. According to the present invention, the first two coding exons of hT1R2 were identified within a PAC by Southern blot. Exon 1 was isolated within a BamHI/BglII fragment that was identified in the Southern experiment, and exon 2 was isolated within a PCR product that spans exon 1 to exon 3. Comparison of the first two coding exons to the rT1R2 sequence established that the two exons encode the N-terminus of the human counterpart to rT1R2. For example, the pairwise amino acid identity between the hT1R2 N-terminal sequence coded by the two exons and corresponding regions of rT1R2 is approximately 72%, whereas the most related annotated sequence in public DNA sequence data banks is only approximately 48% identical to hT1R2. hT1R2 Dredicted cds (SEQ ID NO 20) ATGGGGCCCAGGGCAAAGACCATCTGCTCCCTGTTCTTCCTCCTATGGGTCC (SEQ ID NO. 20) TGGCTGAGCCGGCTGAGAACTCGGACTTCTACCTGCCTGGGGATTACCTCCT GGGTGGCCTCTTCTCCCTCCATGCCAACATGAAGGGCATTGTTCACCTTAAC TTCCTGCAGGTGCCCATGTGCAAGGAGTATGAAGTGAAGGTGATAGGCTACA ACCTCATGCAGGCCATGCGCTTCGCGGTGGAGGAGATCAACAATGACAGCAG CCTGCTGCCTGGTGTGCTGCTGGGCTATGAGATCGTGGATGTGTGCTACATC TCCAACAATGTCCAGCCGGTGCTCTACTTCCTGGCACACGAGGACAACCTCC TTCCCATCCAAGAGGACTACAGTAACTACATTTCCCGTGTGGTGGCTGTCAT TGGCCCTGACAACTCCGAGTCTGTCATGACTGTGGCCAACTTCCTCTCCCTA TTTCTCCTTCCACAGATCACCTACAGCGCCATCAGCGATGAGCTGCGAGACA AGGTGCGCTTCCCGGCTTTGCTGCGTACCACACCCAGCGCCGACCACCACGT CGAGGCCATGGTGCAGCTGATGCTGCACTTCCGCTGGAACTGGATCATTGTG CTGGTGAGCAGCGACACCTATGGCCGCGACAATGGCCAGCTGCTTGGCGAGC GCGTGGCCCGGCGCGACATCTGCATCGCCTTCCAGGAGACGCTGCCCACACT GCAGCCCAACCAGAACATGACGTCAGAGGAGCGCCAGCGCCTGGTGACCATT GTGGACAAGCTGCAGCAGAGCACAGCGCGCGTCGTGGTCGTGTTCTCGCCCG ACCTGACCCTGTACCACTTCTTCAATGAGGTGCTGCGCCAGAACTTCACGGG CGCCGTGTGGATCGCCTCCGAGTCCTGGGCCATCGACCCGGTCCTGCACAAC CTCACGGAGCTGGGCCACTTGGGCACCTTCCTGGGCATCACCATCCAGAGCG TGCCCATCCCGGGCTTCAGTGAGTTCCGCGAGTGGGGCCCACAGGCTGGGCC GCCACCCCTCAGCAGGACCAGCCAGAGCTATACCTGCAACCAGGAGTGCGAC AACTGCCTGAACGCCACCTTGTCCTTCAACACCATTCTCAGGCTCTCTGGGG AGCGTGTCGTCTACAGCGTGTACTCTGCGGTCTATGCTGTGGCCCATGCCCT GCACAGCCTCCTCGGCTGTGACAAAAGCACCTGCACCAAGAGGGTGGTCTAC CCCTGGCAGCTGCTTGAGGAGATCTGGAAGGTCAACTTCACTCTCCTGGACC ACCAAATCTTCTTCGACCCGCAAGGGGACGTGGCTCTGCACTTGGAGATTGT CCAGTGGCAATGGGACCGGAGCCAGAATCCCTTCCAGAGCGTCGCCTCCTAC TACCCCCTGCAGCGACAGCTGAAGAACATCCAAGACATCTCCTGGCACACCG TCAACAACACGATCCCTATGTCCATGTGTTCCAAGAGGTGCCAGTCAGGGCA AAAGAAGAAGCCTGTGGGCATCCACGTCTGCTGCTTCGAGTGCATCGACTGC CTTCCCGGCACCTTCCTCAACCACACTGAAGATGAATATGAATGCCAGGCCT GCCCGAATAACGAGTGGTCCTACCAGAGTGAGACCTCCTGCTTCAAGCGGCA GCTGGTCTTCCTGGAATGGCATGAGGCACCCACCATCGCTGTGGCCCTGCTG GCCGCCCTGGGCTTCCTCAGCACCCTGGCCATCCTGGTGATATTCTGGAGGC ACTTCCAGACACCCATAGTTCGCTCGGCTGGGGGCCCCATGTGCTTCCTGAT GCTGACACTGCTGCTGGTGGCATACATGGTGGTCCCGGTGTACGTGGGGCCG CCCAAGGTCTCCACCTGCCTCTGCCGCCAGGCCCTCTTTCCCCTCTGCTTCA CAATTTGCATCTCCTGTATCGCCGTGCGTTCTTTCCAGATCGTCTGCGCCTT CAAGATGGCCAGCCGCTTCCCACGCGCCTACAGCTACTGGGTCCGCTACCAG GGGCCCTACGTCTCTATGGCATTTATCACGGTACTCAAAATGGTCATTGTGG TAATTGGCATGCTGGCCACGGGCCTCAGTCCCACCACCCGTACTGACCCCGA TGACCCCAAGATCACAATTGTCTCCTGTAACCCCAACTACCGCAACAGCCTG CTGTTCAACACCAGCCTGGACCTGCTGCTCTCAGTGGTGGGTTTCAGCTTCG CCTACATGGGCAAAGAGCTGCCCACCAACTACAACGAGGCCAAGTTCATCAC CCTCAGCATGACCTTCTATTTCACCTCATCCGTCTCCCTCTGCACCTTCATG TCTGCCTACAGCGGGGTGCTGGTCACCATCGTGGACCTCTTGGTCACTGTGC TCAACCTCCTGGCCATCAGCCTGGGCTACTTCGGCCCCAAGTGCTACATGAT CCTCTTCTACCCGGAGCGCAACACGCCCGCCTACTTCAACAGCATGATCCAG GGCTACACCATGAGGAGGGACTAG hT1R2 conceptual translation (SEQ ID NO 21) MGPRAKTICSLFFLLWVLAEPAENSDFYLPGDYLLGGLFSLHANMKGIVHLN (SEQ ID NO. 21) FLQVPMCKEYEVKVIGYNLMQAMRFAVEEINNDSSLLPGVLLGYEIVDVCYI SNNVQPVLYFLAHEDNLLPIQEDYSNYISRVVAVIGPDNSESVMTVANFLSL FLLPQITYSAISDELRDKVRFPALLRTTPSADHHVEAMVQLMLHFRWNWIIV LVSSDTYGRDNGQLLGERVARRDICIAFQETLPTLQPNQNMTSEERQRLVTI VDKLQQSTARVVVVFSPDLTLYHFFNEVLRQNFTGAVWIASESWAIDPVLHN LTELGHLGTFLGITIQSVPIPGFSEFREWGPQAGPPPLSRTSQSYTCNQECD NCLNATLSFNTILRLSGERVVYSVYSAVYAVAHALHSLLGCDKSTCTKRWYP WQLLEEIWKVNFTLLDHQIFFDPQGDVALHLEIVQWQWDRSQNPFQSVASYY PLQRQLKNIQDISWHTVNNTIPMSMCSKRCQSGQKKKPVGIHVCCFECIDCL PGTFLNHTEDEYECQACPNNEWSYQSETSCFKRQLVFLEWHEAPTIAVALLA ALGFLSTLAILVIFWRHFQTPIVRSAGGPMCFLMLTLLLVAYMWPVYVGPPK VSTCLCRQALFPLCFTICISCIAVRSFQIVCAFKMASRFPRAYSYWVRYQGP YVSMAFITVLKMVIWIGMLATGLSPTTRTDPDDPKITIVSCNPNYRNSLLFN TSLDLLLSWGFSFAYMGKELPTNYNEAKFITLSMTFYFTSSVSLCTFMSAYS GVLVTIVDLLVTVLNLLAISLGYFGPKCYMILFYPERNTPAYFNSMIQGYTM RRD

Example 7

[0253] Methods for Heterologous Expression of T1Rs in Heterologous Cells

[0254] An HEK-293 derivative (Chandrashekar et al., Cell 100(6): 703-11 (2000)), which stably expresses Gal 5, was grown and maintained at 37° C. in Dulbecco's Modified Eagle Medium (DMEM, Gibco BRL) supplemented with 10% FBS, MEM non-essential amino acids (Gibco BRL), and 3 μg/ml blasticidin. For calcium-imaging experiments, cells were first seeded onto 24-well tissue-culture plates (approximately 0.1 million cells per well), and transfected by lipofection with Mirus Translt-293 (PanVera). To minimize glutamate-induced and glucose-induced desensitization, supplemented DMEM was replaced with low-glucose DMEM/GlutaMAX (Gibco BRL) approximately 24 hours after transfection. 24 hours later, cells were loaded with the calcium dye Fluo-4 (Molecular Probes), 3 μM in Dulbecco's PBS buffer (DPBS, GibcoBRL), for 1.5 hours at room temperature. After replacement with 250 μl DPBS, stimulation was performed at room temperature by addition of 200 μl DPBS supplemented with taste stimuli. Calcium mobilization was monitored on a Axiovert S100 TV microscope (Zeiss) using Imaging Workbench 4.0 software (Axon). T1R1/T1R3 and T1R2/T1R3 responses were strikingly transient—calcium increases rarely persisted longer than 15 seconds—and asynchronous. The number of responding cells was thus relatively constant over time; therefore, cell responses were quantitated by manually counting the number of responding cells at a fixed time point, typically 30 seconds after stimulus addition.

Example 8

[0255] Human T1R2/T1R3 Functions as a Sweet Taste Receptor

[0256] HEK cells stably expressing Gα15 were transiently transfected with human T1R2, T1R3 and T1R2/T1R3, and assayed for increases in intracellular calcium in response to increasing concentrations of sucrose (FIG. 1(a)). Also, T1R2/T1R3 dose responses were determined for several sweet taste stimuli (FIG. 1(b)). The maximal percentage of responding cells was different for different sweeteners, ranging from 10-30%. For clarity, dose responses were normalized to the maximal percentage of responding cells. The values in FIG. 1 represent the mean±s.e. of four independent responses. X-axis circles mark psychophysical detection thresholds determined by taste testing. Gurmarin (50-full dilution of a filtered 10 g/l Gymnema sylvestre aqueous extract) inhibited the response of T1R2/T1R3 to 250 mM sucrose, but not the response of endogenous β2-adrenergic receptor to 20 μM isoproterenol (FIG. 1(b)). FIG. 1(c) contains the normalized response of T1R2/T1R3 co-expressing cell lines to different sweeteners(sucrose, aspartame, tryptophan and saccharin)

Example 9

[0257] Rat T1R2/T1R3 also Functions as a Sweet Taste Receptor

[0258] HEK cells stably expressing Gal were transiently transfected with hT1R2/hT1R3, rT1R2/rT1R3, hT1R2/rT1R3, and rT1R2/hT1R3. These transfected cells were then assayed for increased intracellular calcium in response to 350 mM sucrose, 25 mM tryptophan, 15 mM aspartame, and 0.05 of monellin. The results with sucrose and aspartame are contained in FIG. 2 and indicate that rT1R2/rT1R3 also functions as a sweet taste receptor. Also, these results suggest that T1R2 may control T1R2/T1R3 ligand specificity.

Example 10

[0259] Human T1R1/T1R3 Functions as Umami Taste Receptors

[0260] HEK cells stably expressing Gα15 were transiently transfected with human T1R1, T1R3 and T1R1/T1R3 and assayed for increases in intracellular calcium in response to increasing concentrations of glutamate (FIG. 3(a) and 0.5 mM glutamate), 0.2 mM IMP, and 0.5 mM glutamate plus 0.2 mM IMP (FIG. 3(b)). Human T1R1/T1R3 dose responses were determined for glutamate in the presence and absence of 0.2 mM IMP (FIG. 3(c)). The maximal percentages of responding cells was approximately 5% for glutamate and approximately 10% for glutamate plus IMP. For clarity, does responses are normalized to the maximal percentage of responding cells. The values represent the mean±s.e. of four independent responses. X-axis circles mark taste detection thresholds determined by taste testing.

Example 11

[0261] PDZIP as an Export Sequence

[0262] The six residue PDZIP sequence (SVSTW (SEQ ID NO:22)) was fused to the C-terminus of hT1R2 and the chimeric receptor (i.e. hT1R2-PDZIP) was transfected into an HEK-293 host cell. The surface expression of hT1R2 was then monitored using immunofluorescence and FACS scanning data. As shown in FIGS. 6A and 6B, the inclusion of the PDZIP sequence increased the surface expression of hT1R2-PDZIP relative to hT1R2.

[0263] PKZIP Sequence

[0264] SVSTVV (SEQ ID NO:22)

[0265] More specifically, FIG. 4A shows an immunofluorescence staining of myc-tagged hT1R2 demonstrating that PDZIP significantly increases the amount of hT1R2 protein on the plasma membrane. FIG. 4B shows FACS analysis data demonstrating the same result.—Cells expressing myc-tagged hT1R2 are indicated by the dotted line and cells expressing myc-tagged hT1R2-PDZIP are indicated by the solid line.

Example 12

[0266] Generation of Cell Lines that Stably Co-Express T1R1/T1R3 or T1R2/T1R3

[0267] Human cell lines that stably co-express human T1R2/T1R3 or human T1R1/T1R3 were generated by transfecting linearized PEAK10-derived (Edge Biosystems) vectors containing pCDNA 3.1/ZEO-derived (Invitrogen) vectors respectively containing hT1R1 or hT1R2 expression construct (plasmid SAV2485 for T1R1, SAV2486 for T1R2) and hT1R3 (plasmid SXV550 for T1R3) into a G_(α15) expressing cell line. Specifically, T1R2/T1R3 stable cell lines were produced by co-transfecting linearized SAV2486 and SXV550 into Aurora Bioscience's HEK-293 cell line that stably expresses G_(α15). T1R1/T1R3 stable cell lines were produced by co-transfecting linearized SAV2485 and SXV550 into the same HEK-293 cell line that stably expresses Ga₁₅. Following SAV2485/SCV550 and SAV2486/SXV550 transfections, puromycin-resistant and zeocin-resistant colonies were selected, expanded, and tested by calcium imaging for responses to sweet or umami taste stimuli. Cells were selected in 0.0005 mg/ml puromycin (CALBIOCHEM) and 0.1 mg/ml zeocin (Invitrogen) at 37° C. in low-glucose DMEM supplemented with GlutaMAX, 10% dialyzed FBS, and 0.003 mg/ml blasticidin. Resistant colonies were expanded, and their responses to sweet taste stimuli evaluated by Fluorescence microscopy. For automated fluorimetric imaging on VIPR-II instrumentation (Aurora Biosciences), T1R2/T1R3 stable cells were first seeded onto 96-well plates (approximately 15,000 cells per well). Twenty-four hours later, cells were loaded with the calcium dye fluo-3-AM (Molecular Probes), 0.005 mM in PBS, for one hour at room temperature. After replacement with 70 ml PBS, stimulation was performed at room temperature by addition of 70 ml PBS supplemented with taste stimuli. Fluorescence (480 nm excitation and 535 nm emission) responses from 20 to 30 seconds following compound addition were averaged, corrected for background fluorescence measured prior to compound addition, and normalized to the response to 0.001 mM ionomycin (CALBIOCHEM), a calcium ionophore.

[0268] It was then observed that when these cell lines were contacted with sweet or umami, that for active clones typically 80-100% of cells responded to taste stimuli. Unexpectedly, the magnitude of individual cell responses was markedly larger than that of transiently transfected cells.

[0269] Based on this observation, the inventors tested the activity of T1R stable cell lines by automated fluorescence imaging using Aurora Bioscience's VIPR instrumentation as described above. The responses of two T1R1/T1R3 and one T1R2/T1R3 cell line are shown in FIG. 5 and FIG. 6 respectively.

[0270] Remarkably, the combination of increased numbers of responding cells and increased response magnitudes resulted in a greater than 10-fold increase in activity relative to transiently transfected cells. (By way of comparison, the percent ionomycin response for cells transiently transfected with T1R2/T1R3 was approximately 5% under optimal conditions.) Moreover, dose responses obtained for stably expressed human T1R2/T1R3 and T1R1/T1R3 correlated with human taste detection thresholds. The robust T1R activity of these stable cell lines suggests that they are well suited for use in high-throughput screening of chemical libraries in order to identify compounds, e.g. small molecules, that modulate the sweet or umami taste receptor and which therefore modulate, enhance, block or mimic sweet or umami taste.

[0271] While the foregoing detailed description has described several embodiments of the present invention, it is to be understood that the above description is illustrative only and not limiting of the disclosed invention. The invention is to be limited only by the claims which follow.

1 24 1 876 DNA Homo sapiens 1 agcctggcag tggcctcagg cagagtctga cgcgcacaaa ctttcaggcc caggaagcga 60 ggacaccact ggggccccag ggtgtggcaa gtgaggatgg caagggtttt gctaaacaaa 120 tcctctgccc gctccccgcc ccgggctcac tccatgtgag gccccagtcg gggcagccac 180 ctgccgtgcc tgttggaagt tgcctctgcc atgctgggcc ctgctgtcct gggcctcagc 240 ctctgggctc tcctgcaccc tgggacgggg gccccattgt gcctgtcaca gcaacttagg 300 atgaaggggg actacgtgct gggggggctg ttccccctgg gcgaggccga ggaggctggc 360 ctccgcagcc ggacacggcc cagcagccct gtgtgcacca ggtacagagg tgggacggcc 420 tgggtcgggg tcagggtgac caggtctggg gtgctcctga gctggggccg aggtggccat 480 ctgcggttct gtgtggcccc aggttctcct caaacggcct gctctgggca ctggccatga 540 aaatggccgt ggaggagatc aacaacaagt cggatctgct gcccgggctg cgcctgggct 600 acgacctctt tgatacgtgc tcggagcctg tggtggccat gaagcccagc ctcatgttcc 660 tggccaaggc aggcagccgc gacatcgccg cctactgcaa ctacacgcag taccagcccc 720 gtgtgctggc tgtcatcggg ccccactcgt cagagctcgc catggtcacc ggcaagttct 780 tcagcttctt cctcatgccc cagtggggcg ccccccacca tcacccaccc ccaaccaacc 840 cctgccccgt gggagcccct tgtgtcagga gaatgc 876 2 2687 DNA Homo sapiens 2 tacatgcacc ccacccagcc ctgccctggg agccctgtgt cagaagatgc tcttggcctt 60 gcaggtcagc tacggtgcta gcatggagct gctgagcgcc cgggagacct tcccctcctt 120 cttccgcacc gtgcccagcg accgtgtgca gctgacggcc gccgcggagc tgctgcagga 180 gttcggctgg aactgggtgg ccgccctggg cagcgacgac gagtacggcc ggcagggcct 240 gagcatcttc tcggccctgg ccgcggcacg cggcatctgc atcgcgcacg agggcctggt 300 gccgctgccc cgtgccgatg actcgcggct ggggaaggtg caggacgtcc tgcaccaggt 360 gaaccagagc agcgtgcagg tggtgctgct gttcgcctcc gtgcacgccg cccacgccct 420 cttcaactac agcatcagca gcaggctctc gcccaaggtg tgggtggcca gcgaggcctg 480 gctgacctct gacctggtca tggggctgcc cggcatggcc cagatgggca cggtgcttgg 540 cttcctccag aggggtgccc agctgcacga gttcccccag tacgtgaaga cgcacctggc 600 cctggccacc gacccggcct tctgctctgc cctgggcgag agggagcagg gtctggagga 660 ggacgtggtg ggccagcgct gcccgcagtg tgactgcatc acgctgcaga acgtgagcgc 720 agggctaaat caccaccaga cgttctctgt ctacgcagct gtgtatagcg tggcccaggc 780 cctgcacaac actcttcagt gcaacgcctc aggctgcccc gcgcaggacc ccgtgaagcc 840 ctggcaggtg agcccgggag atgggggtgt gctgtcctct gcatgtgccc aggccaccag 900 gcacggccac cacgcctgag ctggaggtgg ctggcggctc agccccgtcc cccgcccgca 960 gctcctggag aacatgtaca acctgacctt ccacgtgggc gggctgccgc tgcggttcga 1020 cagcagcgga aacgtggaca tggagtacga cctgaagctg tgggtgtggc agggctcagt 1080 gcccaggctc cacgacgtgg gcaggttcaa cggcagcctc aggacagagc gcctgaagat 1140 ccgctggcac acgtctgaca accaggtgag gtgagggtgg gtgtgccagg cgtgcccgtg 1200 gtagcccccg cggcagggcg cagcctgggg gtgggggccg ttccagtctc ccgtgggcat 1260 gcccagccga gcagagccag accccaggcc tgtgcgcaga agcccgtgtc ccggtgctcg 1320 cggcagtgcc aggagggcca ggtgcgccgg gtcaaggggt tccactcctg ctgctacgac 1380 tgtgtggact gcgaggcggg cagctaccgg caaaacccag gtgagccgcc ttcccggcag 1440 gcgggggtgg gaacgcagca ggggagggtc ctgccaagtc ctgactctga gaccagagcc 1500 cacagggtac aagacgaaca cccagcgccc ttctcctctc tcacagacga catcgcctgc 1560 accttttgtg gccaggatga gtggtccccg gagcgaagca cacgctgctt ccgccgcagg 1620 tctcggttcc tggcatgggg cgagccggct gtgctgctgc tgctcctgct gctgagcctg 1680 gcgctgggcc ttgtgctggc tgctttgggg ctgttcgttc accatcggga cagcccactg 1740 gttcaggcct cgggggggcc cctggcctgc tttggcctgg tgtgcctggg cctggtctgc 1800 ctcagcgtcc tcctgttccc tggccagccc agccctgccc gatgcctggc ccagcagccc 1860 ttgtcccacc tcccgctcac gggctgcctg agcacactct tcctgcaggc ggccgagatc 1920 ttcgtggagt cagaactgcc tctgagctgg gcagaccggc tgagtggctg cctgcggggg 1980 ccctgggcct ggctggtggt gctgctggcc atgctggtgg aggtcgcact gtgcacctgg 2040 tacctggtgg ccttcccgcc ggaggtggtg acggactggc acatgctgcc cacggaggcg 2100 ctggtgcact gccgcacacg ctcctgggtc agcttcggcc tagcgcacgc caccaatgcc 2160 acgctggcct ttctctgctt cctgggcact ttcctggtgc ggagccagcc gggctgctac 2220 aaccgtgccc gtggcctcac ctttgccatg ctggcctact tcatcacctg ggtctccttt 2280 gtgcccctcc tggccaatgt gcaggtggtc ctcaggcccg ccgtgcagat gggcgccctc 2340 ctgctctgtg tcctgggcat cctggctgcc ttccacctgc ccaggtgtta cctgctcatg 2400 cggcagccag ggctcaacac ccccgagttc ttcctgggag ggggccctgg ggatgcccaa 2460 ggccagaatg acgggaacac aggaaatcag gggaaacatg agtgacccaa ccctgtgatc 2520 tcagccccgg tgaacccaga cttagctgcg atccccccca agccagcaat gacccgtgtc 2580 tcgctacaga gaccctcccg ctctaggttc tgaccccagg ttgtctcctg accctgaccc 2640 cacagtgagc cctaggcctg gagcacgtgg acacccctgt gaccatc 2687 3 2559 DNA Homo sapiens 3 atgctgggcc ctgctgtcct gggcctcagc ctctgggctc tcctgcaccc tgggacgggg 60 gccccattgt gcctgtcaca gcaacttagg atgaaggggg actacgtgct gggggggctg 120 ttccccctgg gcgaggccga ggaggctggc ctccgcagcc ggacacggcc cagcagccct 180 gtgtgcacca ggttctcctc aaacggcctg ctctgggcac tggccatgaa aatggccgtg 240 gaggagatca acaacaagtc ggatctgctg cccgggctgc gcctgggcta cgacctcttt 300 gatacgtgct cggagcctgt ggtggccatg aagcccagcc tcatgttcct ggccaaggca 360 ggcagccgcg acatcgccgc ctactgcaac tacacgcagt accagccccg tgtgctggct 420 gtcatcgggc cccactcgtc agagctcgcc atggtcaccg gcaagttctt cagcttcttc 480 ctcatgcccc aggtcagcta cggtgctagc atggagctgc tgagcgcccg ggagaccttc 540 ccctccttct tccgcaccgt gcccagcgac cgtgtgcagc tgacggccgc cgcggagctg 600 ctgcaggagt tcggctggaa ctgggtggcc gccctgggca gcgacgacga gtacggccgg 660 cagggcctga gcatcttctc ggccctggcc gcggcacgcg gcatctgcat cgcgcacgag 720 ggcctggtgc cgctgccccg tgccgatgac tcgcggctgg ggaaggtgca ggacgtcctg 780 caccaggtga accagagcag cgtgcaggtg gtgctgctgt tcgcctccgt gcacgccgcc 840 cacgccctct tcaactacag catcagcagc aggctctcgc ccaaggtgtg ggtggccagc 900 gaggcctggc tgacctctga cctggtcatg gggctgcccg gcatggccca gatgggcacg 960 gtgcttggct tcctccagag gggtgcccag ctgcacgagt tcccccagta cgtgaagacg 1020 cacctggccc tggccaccga cccggccttc tgctctgccc tgggcgagag ggagcagggt 1080 ctggaggagg acgtggtggg ccagcgctgc ccgcagtgtg actgcatcac gctgcagaac 1140 gtgagcgcag ggctaaatca ccaccagacg ttctctgtct acgcagctgt gtatagcgtg 1200 gcccaggccc tgcacaacac tcttcagtgc aacgcctcag gctgccccgc gcaggacccc 1260 gtgaagccct ggcagctcct ggagaacatg tacaacctga ccttccacgt gggcgggctg 1320 ccgctgcggt tcgacagcag cggaaacgtg gacatggagt acgacctgaa gctgtgggtg 1380 tggcagggct cagtgcccag gctccacgac gtgggcaggt tcaacggcag cctcaggaca 1440 gagcgcctga agatccgctg gcacacgtct gacaaccaga agcccgtgtc ccggtgctcg 1500 cggcagtgcc aggagggcca ggtgcgccgg gtcaaggggt tccactcctg ctgctacgac 1560 tgtgtggact gcgaggcggg cagctaccgg caaaacccag acgacatcgc ctgcaccttt 1620 tgtggccagg atgagtggtc cccggagcga agcacacgct gcttccgccg caggtctcgg 1680 ttcctggcat ggggcgagcc ggctgtgctg ctgctgctcc tgctgctgag cctggcgctg 1740 ggccttgtgc tggctgcttt ggggctgttc gttcaccatc gggacagccc actggttcag 1800 gcctcggggg ggcccctggc ctgctttggc ctggtgtgcc tgggcctggt ctgcctcagc 1860 gtcctcctgt tccctggcca gcccagccct gcccgatgcc tggcccagca gcccttgtcc 1920 cacctcccgc tcacgggctg cctgagcaca ctcttcctgc aggcggccga gatcttcgtg 1980 gagtcagaac tgcctctgag ctgggcagac cggctgagtg gctgcctgcg ggggccctgg 2040 gcctggctgg tggtgctgct ggccatgctg gtggaggtcg cactgtgcac ctggtacctg 2100 gtggccttcc cgccggaggt ggtgacggac tggcacatgc tgcccacgga ggcgctggtg 2160 cactgccgca cacgctcctg ggtcagcttc ggcctagcgc acgccaccaa tgccacgctg 2220 gcctttctct gcttcctggg cactttcctg gtgcggagcc agccgggctg ctacaaccgt 2280 gcccgtggcc tcacctttgc catgctggcc tacttcatca cctgggtctc ctttgtgccc 2340 ctcctggcca atgtgcaggt ggtcctcagg cccgccgtgc agatgggcgc cctcctgctc 2400 tgtgtcctgg gcatcctggc tgccttccac ctgcccaggt gttacctgct catgcggcag 2460 ccagggctca acacccccga gttcttcctg ggagggggcc ctggggatgc ccaaggccag 2520 aatgacggga acacaggaaa tcaggggaaa catgagtga 2559 4 852 PRT Homo sapiens 4 Met Leu Gly Pro Ala Val Leu Gly Leu Ser Leu Trp Ala Leu Leu His 1 5 10 15 Pro Gly Thr Gly Ala Pro Leu Cys Leu Ser Gln Gln Leu Arg Met Lys 20 25 30 Gly Asp Tyr Val Leu Gly Gly Leu Phe Pro Leu Gly Glu Ala Glu Glu 35 40 45 Ala Gly Leu Arg Ser Arg Thr Arg Pro Ser Ser Pro Val Cys Thr Arg 50 55 60 Phe Ser Ser Asn Gly Leu Leu Trp Ala Leu Ala Met Lys Met Ala Val 65 70 75 80 Glu Glu Ile Asn Asn Lys Ser Asp Leu Leu Pro Gly Leu Arg Leu Gly 85 90 95 Tyr Asp Leu Phe Asp Thr Cys Ser Glu Pro Val Val Ala Met Lys Pro 100 105 110 Ser Leu Met Phe Leu Ala Lys Ala Gly Ser Arg Asp Ile Ala Ala Tyr 115 120 125 Cys Asn Tyr Thr Gln Tyr Gln Pro Arg Val Leu Ala Val Ile Gly Pro 130 135 140 His Ser Ser Glu Leu Ala Met Val Thr Gly Lys Phe Phe Ser Phe Phe 145 150 155 160 Leu Met Pro Gln Val Ser Tyr Gly Ala Ser Met Glu Leu Leu Ser Ala 165 170 175 Arg Glu Thr Phe Pro Ser Phe Phe Arg Thr Val Pro Ser Asp Arg Val 180 185 190 Gln Leu Thr Ala Ala Ala Glu Leu Leu Gln Glu Phe Gly Trp Asn Trp 195 200 205 Val Ala Ala Leu Gly Ser Asp Asp Glu Tyr Gly Arg Gln Gly Leu Ser 210 215 220 Ile Phe Ser Ala Leu Ala Ala Ala Arg Gly Ile Cys Ile Ala His Glu 225 230 235 240 Gly Leu Val Pro Leu Pro Arg Ala Asp Asp Ser Arg Leu Gly Lys Val 245 250 255 Gln Asp Val Leu His Gln Val Asn Gln Ser Ser Val Gln Val Val Leu 260 265 270 Leu Phe Ala Ser Val His Ala Ala His Ala Leu Phe Asn Tyr Ser Ile 275 280 285 Ser Ser Arg Leu Ser Pro Lys Val Trp Val Ala Ser Glu Ala Trp Leu 290 295 300 Thr Ser Asp Leu Val Met Gly Leu Pro Gly Met Ala Gln Met Gly Thr 305 310 315 320 Val Leu Gly Phe Leu Gln Arg Gly Ala Gln Leu His Glu Phe Pro Gln 325 330 335 Tyr Val Lys Thr His Leu Ala Leu Ala Thr Asp Pro Ala Phe Cys Ser 340 345 350 Ala Leu Gly Glu Arg Glu Gln Gly Leu Glu Glu Asp Val Val Gly Gln 355 360 365 Arg Cys Pro Gln Cys Asp Cys Ile Thr Leu Gln Asn Val Ser Ala Gly 370 375 380 Leu Asn His His Gln Thr Phe Ser Val Tyr Ala Ala Val Tyr Ser Val 385 390 395 400 Ala Gln Ala Leu His Asn Thr Leu Gln Cys Asn Ala Ser Gly Cys Pro 405 410 415 Ala Gln Asp Pro Val Lys Pro Trp Gln Leu Leu Glu Asn Met Tyr Asn 420 425 430 Leu Thr Phe His Val Gly Gly Leu Pro Leu Arg Phe Asp Ser Ser Gly 435 440 445 Asn Val Asp Met Glu Tyr Asp Leu Lys Leu Trp Val Trp Gln Gly Ser 450 455 460 Val Pro Arg Leu His Asp Val Gly Arg Phe Asn Gly Ser Leu Arg Thr 465 470 475 480 Glu Arg Leu Lys Ile Arg Trp His Thr Ser Asp Asn Gln Lys Pro Val 485 490 495 Ser Arg Cys Ser Arg Gln Cys Gln Glu Gly Gln Val Arg Arg Val Lys 500 505 510 Gly Phe His Ser Cys Cys Tyr Asp Cys Val Asp Cys Glu Ala Gly Ser 515 520 525 Tyr Arg Gln Asn Pro Asp Asp Ile Ala Cys Thr Phe Cys Gly Gln Asp 530 535 540 Glu Trp Ser Pro Glu Arg Ser Thr Arg Cys Phe Arg Arg Arg Ser Arg 545 550 555 560 Phe Leu Ala Trp Gly Glu Pro Ala Val Leu Leu Leu Leu Leu Leu Leu 565 570 575 Ser Leu Ala Leu Gly Leu Val Leu Ala Ala Leu Gly Leu Phe Val His 580 585 590 His Arg Asp Ser Pro Leu Val Gln Ala Ser Gly Gly Pro Leu Ala Cys 595 600 605 Phe Gly Leu Val Cys Leu Gly Leu Val Cys Leu Ser Val Leu Leu Phe 610 615 620 Pro Gly Gln Pro Ser Pro Ala Arg Cys Leu Ala Gln Gln Pro Leu Ser 625 630 635 640 His Leu Pro Leu Thr Gly Cys Leu Ser Thr Leu Phe Leu Gln Ala Ala 645 650 655 Glu Ile Phe Val Glu Ser Glu Leu Pro Leu Ser Trp Ala Asp Arg Leu 660 665 670 Ser Gly Cys Leu Arg Gly Pro Trp Ala Trp Leu Val Val Leu Leu Ala 675 680 685 Met Leu Val Glu Val Ala Leu Cys Thr Trp Tyr Leu Val Ala Phe Pro 690 695 700 Pro Glu Val Val Thr Asp Trp His Met Leu Pro Thr Glu Ala Leu Val 705 710 715 720 His Cys Arg Thr Arg Ser Trp Val Ser Phe Gly Leu Ala His Ala Thr 725 730 735 Asn Ala Thr Leu Ala Phe Leu Cys Phe Leu Gly Thr Phe Leu Val Arg 740 745 750 Ser Gln Pro Gly Cys Tyr Asn Arg Ala Arg Gly Leu Thr Phe Ala Met 755 760 765 Leu Ala Tyr Phe Ile Thr Trp Val Ser Phe Val Pro Leu Leu Ala Asn 770 775 780 Val Gln Val Val Leu Arg Pro Ala Val Gln Met Gly Ala Leu Leu Leu 785 790 795 800 Cys Val Leu Gly Ile Leu Ala Ala Phe His Leu Pro Arg Cys Tyr Leu 805 810 815 Leu Met Arg Gln Pro Gly Leu Asn Thr Pro Glu Phe Phe Leu Gly Gly 820 825 830 Gly Pro Gly Asp Ala Gln Gly Gln Asn Asp Gly Asn Thr Gly Asn Gln 835 840 845 Gly Lys His Glu 850 5 23 DNA Artificial Sequence Description of Artificial Sequence Primer 5 cgnttyytng cntggggnga rcc 23 6 23 DNA Artificial Sequence Description of Artificial Sequence Primer 6 cgngcncgrt trtarcancc ngg 23 7 9 PRT Homo sapiens 7 Arg Phe Leu Ala Trp Gly Glu Pro Ala 1 5 8 8 PRT Homo sapiens 8 Pro Gly Cys Tyr Asn Arg Ala Arg 1 5 9 552 DNA Mus sp. 9 gtgctgtcac tcctcctgct gctttgcctg gtgctgggtc tagcactggc tgctctgggg 60 ctctctgtcc accactggga cagccctctt gtccaggcct caggcggctc acagttctgc 120 tttggcctga tctgcctagg cctcttctgc ctcagtgtcc ttctgttccc aggacggcca 180 agctctgcca gctgccttgc acaacaacca atggctcacc tccctctcac aggctgcctg 240 agcacactct tcctgcaagc agctgagacc tttgtggagt ctgagctgcc actgagctgg 300 gcaaactggc tatgcagcta ccttcgggac tctggcctgc tagtggtact gttggccact 360 tttgtggagg cagcactatg tgcctggtat ttgaccgctt caccagaagt ggtgacagac 420 tggtcagtgc tgcccacaga ggtactggag cactgccacg tgcgttcctg ggtcaacctg 480 ggcttggtgc acatcaccaa tgcaatggta gcttttctct gctttctggg cactttcctg 540 gtacaagacc ag 552 10 184 PRT Mus sp. 10 Val Leu Ser Leu Leu Leu Leu Leu Cys Leu Val Leu Gly Leu Ala Leu 1 5 10 15 Ala Ala Leu Gly Leu Ser Val His His Trp Asp Ser Pro Leu Val Gln 20 25 30 Ala Ser Gly Gly Ser Gln Phe Cys Phe Gly Leu Ile Cys Leu Gly Leu 35 40 45 Phe Cys Leu Ser Val Leu Leu Phe Pro Gly Arg Pro Ser Ser Ala Ser 50 55 60 Cys Leu Ala Gln Gln Pro Met Ala His Leu Pro Leu Thr Gly Cys Leu 65 70 75 80 Ser Thr Leu Phe Leu Gln Ala Ala Glu Thr Phe Val Glu Ser Glu Leu 85 90 95 Pro Leu Ser Trp Ala Asn Trp Leu Cys Ser Tyr Leu Arg Asp Ser Gly 100 105 110 Leu Leu Val Val Leu Leu Ala Thr Phe Val Glu Ala Ala Leu Cys Ala 115 120 125 Trp Tyr Leu Thr Ala Ser Pro Glu Val Val Thr Asp Trp Ser Val Leu 130 135 140 Pro Thr Glu Val Leu Glu His Cys His Val Arg Ser Trp Val Asn Leu 145 150 155 160 Gly Leu Val His Ile Thr Asn Ala Met Val Ala Phe Leu Cys Phe Leu 165 170 175 Gly Thr Phe Leu Val Gln Asp Gln 180 11 558 DNA Rattus sp. 11 gtgctgtcac ttctcctgct gctttgcctg gtgctgggcc tgacactggc tgccctgggg 60 ctctttgtcc actactggga cagccctctt gttcaggcct caggtgggtc actgttctgc 120 tttggcctga tctgcctagg cctcttctgc ctcagtgtcc ttctgttccc aggacgacca 180 cgctctgcca gctgccttgc ccaacaacca atggctcacc tccctctcac aggctgcctg 240 agcacactct tcctgcaagc agccgagatc tttgtggagt ctgagctgcc actgagttgg 300 gcaaactggc tctgcagcta ccttcggggc ccctgggctt ggctggtggt actgctggcc 360 actcttgtgg aggctgcact atgtgcctgg tacttgatgg ctttccctcc agaggtggtg 420 acagattggc aggtgctgcc cacggaggta ctggaacact gccgcatgcg ttcctgggtc 480 agcctgggct tggtgcacat caccaatgca ggggtagctt tcctctgctt tctgggcact 540 ttcctggtac aaagccag 558 12 186 PRT Rattus sp. 12 Val Leu Ser Leu Leu Leu Leu Leu Cys Leu Val Leu Gly Leu Thr Leu 1 5 10 15 Ala Ala Leu Gly Leu Phe Val His Tyr Trp Asp Ser Pro Leu Val Gln 20 25 30 Ala Ser Gly Gly Ser Leu Phe Cys Phe Gly Leu Ile Cys Leu Gly Leu 35 40 45 Phe Cys Leu Ser Val Leu Leu Phe Pro Gly Arg Pro Arg Ser Ala Ser 50 55 60 Cys Leu Ala Gln Gln Pro Met Ala His Leu Pro Leu Thr Gly Cys Leu 65 70 75 80 Ser Thr Leu Phe Leu Gln Ala Ala Glu Ile Phe Val Glu Ser Glu Leu 85 90 95 Pro Leu Ser Trp Ala Asn Trp Leu Cys Ser Tyr Leu Arg Gly Pro Trp 100 105 110 Ala Trp Leu Val Val Leu Leu Ala Thr Leu Val Glu Ala Ala Leu Cys 115 120 125 Ala Trp Tyr Leu Met Ala Phe Pro Pro Glu Val Val Thr Asp Trp Gln 130 135 140 Val Leu Pro Thr Glu Val Leu Glu His Cys Arg Met Arg Ser Trp Val 145 150 155 160 Ser Leu Gly Leu Val His Ile Thr Asn Ala Gly Val Ala Phe Leu Cys 165 170 175 Phe Leu Gly Thr Phe Leu Val Gln Ser Gln 180 185 13 2577 DNA Rattus sp. 13 atgccgggtt tggctatctt gggcctcagt ctggctgctt tcctggagct tgggatgggg 60 tcctctttgt gtctgtcaca gcaattcaag gcacaagggg actatatatt gggtggacta 120 tttcccctgg gcacaactga ggaggccact ctcaaccaga gaacacagcc caacggcatc 180 ctatgtacca ggttctcgcc ccttggtttg ttcctggcca tggctatgaa gatggctgta 240 gaggagatca acaatggatc tgccttgctc cctgggctgc gactgggcta tgacctgttt 300 gacacatgct cagagccagt ggtcaccatg aagcccagcc tcatgttcat ggccaaggtg 360 ggaagtcaaa gcattgctgc ctactgcaac tacacacagt accaaccccg tgtgctggct 420 gtcattggtc cccactcatc agagcttgcc ctcattacag gcaagttctt cagcttcttc 480 ctcatgccac aggtcagcta tagtgccagc atggatcggc taagtgaccg ggaaacattt 540 ccatccttct tccgcacagt gcccagtgac cgggtgcagc tgcaggccgt tgtgacactg 600 ttgcagaatt tcagctggaa ctgggtggct gccttaggta gtgatgatga ctatggccgg 660 gaaggtctga gcatcttttc tggtctggcc aactcacgag gtatctgcat tgcacacgag 720 ggcctggtgc cacaacatga cactagtggc caacaattgg gcaaggtggt ggatgtgcta 780 cgccaagtga accaaagcaa agtacaggtg gtggtgctgt ttgcatctgc ccgtgctgtc 840 tactcccttt ttagctacag catccttcat gacctctcac ccaaggtatg ggtggccagt 900 gagtcctggc tgacctctga cctggtcatg acacttccca atattgcccg tgtgggcact 960 gttcttgggt ttctgcagcg cggtgcccta ctgcctgaat tttcccatta tgtggagact 1020 cgccttgccc tagctgctga cccaacattc tgtgcctccc tgaaagctga gttggatctg 1080 gaggagcgcg tgatggggcc acgctgttca caatgtgact acatcatgct acagaacctg 1140 tcatctgggc tgatgcagaa cctatcagct gggcagttgc accaccaaat atttgcaacc 1200 tatgcagctg tgtacagtgt ggctcaggcc cttcacaaca ccctgcagtg caatgtctca 1260 cattgccaca catcagagcc tgttcaaccc tggcagctcc tggagaacat gtacaatatg 1320 agtttccgtg ctcgagactt gacactgcag tttgatgcca aagggagtgt agacatggaa 1380 tatgacctga agatgtgggt gtggcagagc cctacacctg tactacatac tgtaggcacc 1440 ttcaacggca cccttcagct gcagcactcg aaaatgtatt ggccaggcaa ccaggtgcca 1500 gtctcccagt gctcccggca gtgcaaagat ggccaggtgc gcagagtaaa gggctttcat 1560 tcctgctgct atgactgtgt ggactgcaag gcagggagct accggaagca tccagatgac 1620 ttcacctgta ctccatgtgg caaggatcag tggtccccag aaaaaagcac aacctgctta 1680 cctcgcaggc ccaagtttct ggcttggggg gagccagctg tgctgtcact tctcctgctg 1740 ctttgcctgg tgctgggcct gacactggct gccctggggc tctttgtcca ctactgggac 1800 agccctcttg ttcaggcctc aggtgggtca ctgttctgct ttggcctgat ctgcctaggc 1860 ctcttctgcc tcagtgtcct tctgttccca ggacgaccac gctctgccag ctgccttgcc 1920 caacaaccaa tggctcacct ccctctcaca ggctgcctga gcacactctt cctgcaagca 1980 gccgagatct ttgtggagtc tgagctgcca ctgagttggg caaactggct ctgcagctac 2040 cttcggggcc cctgggcttg gctggtggta ctgctggcca ctcttgtgga ggctgcacta 2100 tgtgcctggt acttgatggc tttccctcca gaggtggtga cagattggca ggtgctgccc 2160 acggaggtac tggaacactg ccgcatgcgt tcctgggtca gcctgggctt ggtgcacatc 2220 accaatgcag tgttagcttt cctctgcttt ctgggcactt tcctggtaca gagccagcct 2280 ggtcgctata accgtgcccg tggcctcacc ttcgccatgc tagcttattt catcatctgg 2340 gtctcttttg tgcccctcct ggctaatgtg caggtggcct accagccagc tgtgcagatg 2400 ggtgctatct tattctgtgc cctgggcatc ctggccacct tccacctgcc caaatgctat 2460 gtacttctgt ggctgccaga gctcaacacc caggagttct tcctgggaag gagccccaag 2520 gaagcatcag atgggaatag tggtagtagt gaggcaactc ggggacacag tgaatga 2577 14 858 PRT Rattus sp. 14 Met Pro Gly Leu Ala Ile Leu Gly Leu Ser Leu Ala Ala Phe Leu Glu 1 5 10 15 Leu Gly Met Gly Ser Ser Leu Cys Leu Ser Gln Gln Phe Lys Ala Gln 20 25 30 Gly Asp Tyr Ile Leu Gly Gly Leu Phe Pro Leu Gly Thr Thr Glu Glu 35 40 45 Ala Thr Leu Asn Gln Arg Thr Gln Pro Asn Gly Ile Leu Cys Thr Arg 50 55 60 Phe Ser Pro Leu Gly Leu Phe Leu Ala Met Ala Met Lys Met Ala Val 65 70 75 80 Glu Glu Ile Asn Asn Gly Ser Ala Leu Leu Pro Gly Leu Arg Leu Gly 85 90 95 Tyr Asp Leu Phe Asp Thr Cys Ser Glu Pro Val Val Thr Met Lys Pro 100 105 110 Ser Leu Met Phe Met Ala Lys Val Gly Ser Gln Ser Ile Ala Ala Tyr 115 120 125 Cys Asn Tyr Thr Gln Tyr Gln Pro Arg Val Leu Ala Val Ile Gly Pro 130 135 140 His Ser Ser Glu Leu Ala Leu Ile Thr Gly Lys Phe Phe Ser Phe Phe 145 150 155 160 Leu Met Pro Gln Val Ser Tyr Ser Ala Ser Met Asp Arg Leu Ser Asp 165 170 175 Arg Glu Thr Phe Pro Ser Phe Phe Arg Thr Val Pro Ser Asp Arg Val 180 185 190 Gln Leu Gln Ala Val Val Thr Leu Leu Gln Asn Phe Ser Trp Asn Trp 195 200 205 Val Ala Ala Leu Gly Ser Asp Asp Asp Tyr Gly Arg Glu Gly Leu Ser 210 215 220 Ile Phe Ser Gly Leu Ala Asn Ser Arg Gly Ile Cys Ile Ala His Glu 225 230 235 240 Gly Leu Val Pro Gln His Asp Thr Ser Gly Gln Gln Leu Gly Lys Val 245 250 255 Val Asp Val Leu Arg Gln Val Asn Gln Ser Lys Val Gln Val Val Val 260 265 270 Leu Phe Ala Ser Ala Arg Ala Val Tyr Ser Leu Phe Ser Tyr Ser Ile 275 280 285 Leu His Asp Leu Ser Pro Lys Val Trp Val Ala Ser Glu Ser Trp Leu 290 295 300 Thr Ser Asp Leu Val Met Thr Leu Pro Asn Ile Ala Arg Val Gly Thr 305 310 315 320 Val Leu Gly Phe Leu Gln Arg Gly Ala Leu Leu Pro Glu Phe Ser His 325 330 335 Tyr Val Glu Thr Arg Leu Ala Leu Ala Ala Asp Pro Thr Phe Cys Ala 340 345 350 Ser Leu Lys Ala Glu Leu Asp Leu Glu Glu Arg Val Met Gly Pro Arg 355 360 365 Cys Ser Gln Cys Asp Tyr Ile Met Leu Gln Asn Leu Ser Ser Gly Leu 370 375 380 Met Gln Asn Leu Ser Ala Gly Gln Leu His His Gln Ile Phe Ala Thr 385 390 395 400 Tyr Ala Ala Val Tyr Ser Val Ala Gln Ala Leu His Asn Thr Leu Gln 405 410 415 Cys Asn Val Ser His Cys His Thr Ser Glu Pro Val Gln Pro Trp Gln 420 425 430 Leu Leu Glu Asn Met Tyr Asn Met Ser Phe Arg Ala Arg Asp Leu Thr 435 440 445 Leu Gln Phe Asp Ala Lys Gly Ser Val Asp Met Glu Tyr Asp Leu Lys 450 455 460 Met Trp Val Trp Gln Ser Pro Thr Pro Val Leu His Thr Val Gly Thr 465 470 475 480 Phe Asn Gly Thr Leu Gln Leu Gln His Ser Lys Met Tyr Trp Pro Gly 485 490 495 Asn Gln Val Pro Val Ser Gln Cys Ser Arg Gln Cys Lys Asp Gly Gln 500 505 510 Val Arg Arg Val Lys Gly Phe His Ser Cys Cys Tyr Asp Cys Val Asp 515 520 525 Cys Lys Ala Gly Ser Tyr Arg Lys His Pro Asp Asp Phe Thr Cys Thr 530 535 540 Pro Cys Gly Lys Asp Gln Trp Ser Pro Glu Lys Ser Thr Thr Cys Leu 545 550 555 560 Pro Arg Arg Pro Lys Phe Leu Ala Trp Gly Glu Pro Ala Val Leu Ser 565 570 575 Leu Leu Leu Leu Leu Cys Leu Val Leu Gly Leu Thr Leu Ala Ala Leu 580 585 590 Gly Leu Phe Val His Tyr Trp Asp Ser Pro Leu Val Gln Ala Ser Gly 595 600 605 Gly Ser Leu Phe Cys Phe Gly Leu Ile Cys Leu Gly Leu Phe Cys Leu 610 615 620 Ser Val Leu Leu Phe Pro Gly Arg Pro Arg Ser Ala Ser Cys Leu Ala 625 630 635 640 Gln Gln Pro Met Ala His Leu Pro Leu Thr Gly Cys Leu Ser Thr Leu 645 650 655 Phe Leu Gln Ala Ala Glu Ile Phe Val Glu Ser Glu Leu Pro Leu Ser 660 665 670 Trp Ala Asn Trp Leu Cys Ser Tyr Leu Arg Gly Pro Trp Ala Trp Leu 675 680 685 Val Val Leu Leu Ala Thr Leu Val Glu Ala Ala Leu Cys Ala Trp Tyr 690 695 700 Leu Met Ala Phe Pro Pro Glu Val Val Thr Asp Trp Gln Val Leu Pro 705 710 715 720 Thr Glu Val Leu Glu His Cys Arg Met Arg Ser Trp Val Ser Leu Gly 725 730 735 Leu Val His Ile Thr Asn Ala Val Leu Ala Phe Leu Cys Phe Leu Gly 740 745 750 Thr Phe Leu Val Gln Ser Gln Pro Gly Arg Tyr Asn Arg Ala Arg Gly 755 760 765 Leu Thr Phe Ala Met Leu Ala Tyr Phe Ile Ile Trp Val Ser Phe Val 770 775 780 Pro Leu Leu Ala Asn Val Gln Val Ala Tyr Gln Pro Ala Val Gln Met 785 790 795 800 Gly Ala Ile Leu Phe Cys Ala Leu Gly Ile Leu Ala Thr Phe His Leu 805 810 815 Pro Lys Cys Tyr Val Leu Leu Trp Leu Pro Glu Leu Asn Thr Gln Glu 820 825 830 Phe Phe Leu Gly Arg Ser Pro Lys Glu Ala Ser Asp Gly Asn Ser Gly 835 840 845 Ser Ser Glu Ala Thr Arg Gly His Ser Glu 850 855 15 8194 DNA Homo sapiens modified_base (1251)..(1300) a, t, c, g, other or unknown 15 gagaatctcg cgagatcccg tcggtccgcc ccgctgccct cccagctgcc gaaaagaggg 60 gcctccgagc cgccggcgcc ctctgccggc aacctccgga agcacactag gaggttccag 120 ccgatctggt cgaggggctc cacggaggac tccatttacg ttacgcaaat tccctacccc 180 agccggccgg agagagaaag ccagaaacct cgcgaccagc catgggccac ctctccggaa 240 aaacaccggg atattttttt tctcctgcag aaaaagcttt aggattggca gtttaaacaa 300 aacatgtcta tttgcatacc ttcggtttgc atgcatttgt ttcgaagtga gcaaccctgg 360 gtaacaaggc gaaagtatat gacaatttgc tcagaatctt aatgtcagaa aactggagac 420 tggggcaggg gggtgtcgac tcaaagctgt gtctcattta gtaaactgag gcccaggtaa 480 aaagttctga aacctcgcaa cacccggaga aattgtgttc cagcctccca cctcgcccca 540 aaatgccaga gctccttttc taagccaggt gaagtcacag agcgtggaca gaacccacaa 600 ccgtccagag gaagggtcac tgggtgccac ctggtttgca tctgtgcctt cgtcctgccc 660 agttcctgag tgggaccgca ggcccggaat gtcaaggcaa acagtcctgc ttcagccact 720 gggctccagt cccacccctt ttgggggcct gaagttagga agcatccggc agctgccttc 780 tatttaagca actggcctcc ttagaggcca ctccttggcc atgccaggcg cgggcatctg 840 gccagcatgc tgctctgcac ggctcgcctg gtcggcctgc agcttctcat ttcctgctgc 900 tgggcctttg cctgccatag cacggagtct tctcctgact tcaccctccc cggagattac 960 ctcctggcag gcctgttccc tctccattct ggctgtctgc aggtgaggca cagacccgag 1020 gtgaccctgt gtgacaggtg agtgaggggc cagcagagcc acacttagtg ggacccctgg 1080 ctatagggcc cctctggctg ccatcctcca aacaggacct tgcctctgcc tttgcccctt 1140 gaactgtccc caggccttgt tcatcaatcc acttgccacc taagtgctgg ctagaccttc 1200 ctagacactt cggccagttt ccaattattt cacccttgct gttagaatgt nnnnnnnnnn 1260 nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn aattccttaa actaaatttc 1320 tcactttctc tctctctctg gaaaacactg actaatgtag caggtttctc tgctccagga 1380 cttcaggacc ttttcgatgc taataagttt ctccatcagg gccagcttgt tcctcctact 1440 gagcttgaga gcccttgttg aagttgtggt ttgggggact ggaccgatga cctcaaaggt 1500 tccctttgct cccaagcctc agagtctagg aggccagagg gtctcagcag gcctttgtcc 1560 ttctcagctg tctcttactg gctttctcca caggtcttgt agcttcaatg agcatggcta 1620 ccacctcttc caggctatgc ggcttggggt tgaggagata aacaactcca cggccctgct 1680 gcccaacatc accctggggt accagctgta tgatgtgtgt tctgactctg ccaatgtgta 1740 tgccacgctg agagtgctct ccctgccagg gcaacaccac atagagctcc aaggagacct 1800 tctccactat tcccctacgg tgctggcagt gattgggcct gacagcacca accgtgctgc 1860 caccacagcc gccctgctga gccctttcct ggtgcccatg gtaagctgga gcctcagacc 1920 tttgcccatc tcccttcagg caagtctggg nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn 1980 nnnnnnnnnn nnnnnnnnnn gccaccatgc ccggctaatt tttttgtatt tttagtagag 2040 acggggtttc accgtgttag ccaggctggt cgcaaactcc taacctcgtg atccacccac 2100 ctcggcctcc caatgtgctg ggattacagg tgtgagccac tgcacccggc cataatgtat 2160 taatataata aaataattat acaactcacc ataatgtaga atcagtggga gccctgagct 2220 tgttttccta caactagatg gtcccatctg ggggtgatgg gagacagtga cagatcatca 2280 gacattagat tctcataagt agcgtgcaac ccagatccct cgcatgtgca gttcacagta 2340 gggttcaagc tcctacaaga atctgatgct gctgctgatc tgacaggagg ggagcagctg 2400 taaatacaga tgaagcttcg cttactcacc agctgctcac ctcctcctgt gaggcccggt 2460 tcctaacagg ccactgacct aacttctgcc ctgacctaca catgcttctc ttcttccttg 2520 caaactgcct ccagtggaag tccctgaagg tccccaaaca cacgggacta tttcactcct 2580 atgcaggttt tgtctccttt gcttggaatg catcccctca ccccttgtcc ccaggcagat 2640 tcccacccct cccccagaac ctgccccagt ggagccttcg caggtgattt gtcagtttca 2700 caggctgagg ggtgctctcc tggtctcccc ggctccctgt atccccacac ccagcacagg 2760 gccaggcact gggggggcct tcagtggaga ctgaaatggc tgaacgggac ctcccataga 2820 ttagctatgc ggccagcagc gagacgctca gcgtgaagcg gcagtatccc tctttcctgc 2880 gcaccatccc caatgacaag taccaggtgg agaccatggt gctgctgctg cagaagttcg 2940 ggtggacctg gatctctctg gttggcagca gtgacgacta tgggcagcta ggggtgcagg 3000 cactggagaa ccaggccact ggtcagggga tctgcattgc tttcaaggac atcatgccct 3060 tctctgccca ggtgggcgat gagaggatgc agtgcctcat gcgccacctg gcccaggccg 3120 gggccaccgt cgtggttgtt ttttccagcc ggcagttggc cagggtgttt ttcgagtccg 3180 tggtgctgac caacctgact ggcaaggtgt gggtcgcctc agaagcctgg gccctctcca 3240 ggcacatcac tggggtgccc gggatccagc gcattgggat ggtgctgggc gtggccatcc 3300 agaagagggc tgtccctggc ctgaaggcgt ttgaagaagc ctatgcccgg gcagacaaga 3360 aggcccctag gccttgccac aagggctcct ggtgcagcag caatcagctc tgcagagaat 3420 gccaagcttt catggcacac acgatgccca agctcaaagc cttctccatg agttctgcct 3480 acaacgcata ccgggctgtg tatgcggtgg cccatggcct ccaccagctc ctgggctgtg 3540 cctctggagc ttgttccagg ggccgagtct acccctggca ggtaagagag cccaccccag 3600 cacctcctgt cagggagaac agccaatcct gagatgagca gagtgggcac tctccggtca 3660 ctctaaatgc caagggggat aaatgccact aacttgaggt tttttgtttt gttttgtttt 3720 gttttttgag acagtctggc tctgtcaccc aggctgcagt gtagtgatgc gatctcggct 3780 ctctgcaact tccacctcct gggttcaagt gattctcttg cctcggcctc ctgagtagct 3840 gggattacag gcacccacca ccatgcctgg ataatttttc ttttcttttt tttttttttg 3900 agatagagtc tcgctctgtt gcccaggctg gaatgcagtg gtgcgatctt ggctcactgt 3960 gagctccgcc tcccaggttc actccattcc cctgcctcag cctcccaagt aggtgggact 4020 acgggcgccc gccaccacgc ccagctaatt ttttttgtat tttgagtaga gacggggttt 4080 caccatgtta gccaggatgg tctcaatctc ctgaccttgt catccgccca cctcgtcctc 4140 ccaaagtgct gggattacag gcgtgagcca ccgcacccgg cctaattttt gtatttttag 4200 tagagatggg gtttcaccat gttggccagg ctggtctcga actcctggca tcaagtgatc 4260 ctcctgcttc ggcctcccaa agtgctggga ttacaggcat tagctctctt ctcttagaca 4320 gatctttctc tctgatcctt gccttctctc acccactgtg tcttggaagt gtcaagtgat 4380 aagatccagg gctaaaactg tctgtaaagg agtgtttgtt agaggcctcc tctcaggagg 4440 ttggtgggga agattgaggg gcttcctaag aaggaaggga cgagaccttc ctgatgggct 4500 gaaaccacca ggacggaaac ccaggaaggc cccaggccct tgcttctggg accatgtggg 4560 tctgtgctgt ctgtggtggc ttcatgatac gcgtttcttt cagcttttgg agcagatcca 4620 caaggtgcat ttccttctac acaaggacac tgtggcgttt aatgacaaca gagatcccct 4680 cagtagctat aacataattg cctgggactg gaatggaccc aagtggacct tcacggtcct 4740 cggttcctcc acatggtctc cagttcagct aaacataaat gagaccaaaa tccagtggca 4800 cggaaaggac aaccaggtaa tggggatgtg gctactcacc atgtaactgg cttatgggca 4860 acctagagcc tgggggtgat gctgacacag tgtacaggga gcaggagggg ggccccaggg 4920 gtccagctgc caccactcta cccatcctgg ccagggaagc agggaagaca ctccgtaggc 4980 gagtgtgcag atgccctggg gcggaagttc acacgaccag gggccctgcc ctgggagtga 5040 gccctgaggg cagatgcaca gagattctgt tttctgttcc acatgtgagc tgtcctttga 5100 cttgggcccc tacgtgtggc ccctctggct tcttacaggt gcctaagtct gtgtgttcca 5160 gcgactgtct tgaagggcac cagcgagtgg ttacgggttt ccatcactgc tgctttgagt 5220 gtgtgccctg tggggctggg accttcctca acaagagtgg tgagtgggca atggagcagg 5280 cgagctaccc agcactcccg ggggctgcac ggtggaggga gggcctccct tgggccccat 5340 gtgccctgcc ccagaaccaa ggcccagtca ctgggctgcc agttagcttc aggttggagg 5400 acacctgcta ccagacagaa ttctgatcaa gagaatcagc cactgggtgc ggtggctcat 5460 gcctgtaatc ccagcacttt gggaggctga ggcgggtgga tcacttgagg tcgggagttc 5520 gagaccagcc tggccaacat ggtgaaaccc catctctacc aaaaatataa aaaattagct 5580 gggtgtggtg gcgcgtgcct gtaatcccag ctactcggga ggctgaggca ggagaatcac 5640 ttgaacccag gaggcggagg ttgcagtgag ccaagatgca ttccagcctg gaccacaaag 5700 cgagaattcg tccccccaaa aaaagaaagg aggccgggcg cggtggctca cacctgtaat 5760 cccagcactt tgggaggccg aggtgggtgg atcacctgag gtcaggagtt cgagaccagc 5820 ctgaccaaca tggtgaaacc ccatctctac taaaaataca aaaaaagtta gccgggcgtt 5880 gtggcgtgtg cctgtaattc cagctactcg ggaggctgag gcaggagaat tgcttgaacc 5940 cgggaggcgg aggttgcagt gagccaagat tgcaccattg cactccagcc tgggcgacaa 6000 gagaaaaact ctgtctcaaa aaaaaagaaa gaaagaaaga attagccaac tgaaagcctt 6060 agactgaggt gtgtcctctg ttagagagct gtcatcacaa ctcctacaaa agcagtcgta 6120 tcctgaattc aacctctttc tctaaatgaa tatagctatt gttccctttg tgccctcttg 6180 tcctactgtc ccttctgttg cccatgccaa agacagctag ctccttgaac agcttggcct 6240 gaatacagat actagcgtgt ctgcagcaga gaaaaaaaca gcattcccca tccagaaatg 6300 caaggtcaag aacagagagc aaattaggta gctaaggact caggtcctta gttggtgtcc 6360 aggggccaca ttctttcctt tcaccatctc tgtagggaca ggaatacttc ccttctgtcc 6420 tcagagggtc aggactcaga gaaaccacag agcagcagct caggaaagtg gttcatggaa 6480 atgctggcaa gagagagggg ttacaatgcc ctcccttggg agcaggctgc tcccatcaga 6540 tcgtaacctc tctggtatgt gggcagagct accaggttaa ggtcctccct agggtttgca 6600 aaaccctcat gggatcatga gccatacaga accgacctgt gtgtctccag agtctgtaat 6660 taacacaggc attttgagga aatgcgtggc ctcaggcccc actcccggct acccccatcc 6720 cactatgcct agtatagtct agctgccctg gtacaattct cccagtatct tgcaggcccc 6780 tatttcctat tcctactctg ctcatctggc tctcaggaac cttcttggcc ttccctttca 6840 gacctctaca gatgccagcc ttgtgggaaa gaagagtggg cacctgaggg aagccagacc 6900 tgcttcccgc gcactgtggt gtttttggct ttgcgtgagc acacctcttg ggtgctgctg 6960 gcagctaaca cgctgctgct gctgctgctg cttgggactg ctggcctgtt tgcctggcac 7020 ctagacaccc ctgtggtgag gtcagcaggg ggccgcctgt gctttcttat gctgggctcc 7080 ctggcagcag gtagtggcag cctctatggc ttctttgggg aacccacaag gcctgcgtgc 7140 ttgctacgcc aggccctctt tgcccttggt ttcaccatct tcctgtcctg cctgacagtt 7200 cgctcattcc aactaatcat catcttcaag ttttccacca aggtacctac attctaccac 7260 gcctgggtcc aaaaccacgg tgctggcctg tttgtgatga tcagctcagc ggcccagctg 7320 cttatctgtc taacttggct ggtggtgtgg accccactgc ctgctaggga ataccagcgc 7380 ttcccccatc tggtgatgct tgagtgcaca gagaccaact ccctgggctt catactggcc 7440 ttcctctaca atggcctcct ctccatcagt gcctttgcct gcagctacct gggtaaggac 7500 ttgccagaga actacaacga ggccaaatgt gtcaccttca gcctgctctt caacttcgtg 7560 tcctggatcg ccttcttcac cacggccagc gtctacgacg gcaagtacct gcctgcggcc 7620 aacatgatgg ctgggctgag cagcctgagc agcggcttcg gtgggtattt tctgcctaag 7680 tgctacgtga tcctctgccg cccagacctc aacagcacag agcacttcca ggcctccatt 7740 caggactaca cgaggcgctg cggctccacc tgaccagtgg gtcagcaggc acggctggca 7800 gccttctctg ccctgagggt cgaaggtcga gcaggccggg ggtgtccggg aggtctttgg 7860 gcatcgcggt ctggggttgg gacgtgtaag cgcctgggag agcctagacc aggctccggg 7920 ctgccaataa agaagtgaaa tgcgtatctg gtctcctgtc gtgggagagt gtgaggtgta 7980 acggattcaa gtctgaaccc agagcctgga aaaggctgac cgcccagatt gacgttgcta 8040 ggcaactccg gaggcgggcc cagcgccaaa agaacagggc gaggcgtcgt ccccgcatcc 8100 cattggccgt tctctgcggg gccccgccct cgggggccgg agctagaagc tctacgcttc 8160 cgaggcgcac ctcctggcct gcacgctttg acgt 8194 16 2526 DNA Homo sapiens 16 atgctgctct gcacggctcg cctggtcggc ctgcagcttc tcatttcctg ctgctgggcc 60 tttgcctgcc atagcacgga gtcttctcct gacttcaccc tccccggaga ttacctcctg 120 gcaggcctgt tccctctcca ttctggctgt ctgcaggtga ggcacagacc cgaggtgacc 180 ctgtgtgaca ggtcttgtag cttcaatgag catggctacc acctcttcca ggctatgcgg 240 cttggggttg aggagataaa caactccacg gccctgctgc ccaacatcac cctggggtac 300 cagctgtatg atgtgtgttc tgactctgcc aatgtgtatg ccacgctgag agtgctctcc 360 ctgccagggc aacaccacat agagctccaa ggagaccttc tccactattc ccctacggtg 420 ctggcagtga ttgggcctga cagcaccaac cgtgctgcca ccacagccgc cctgctgagc 480 cctttcctgg tgcccatgat tagctatgcg gccagcagcg agacgctcag cgtgaagcgg 540 cagtatccct ctttcctgcg caccatcccc aatgacaagt accaggtgga gaccatggtg 600 ctgctgctgc agaagttcgg gtggacctgg atctctctgg ttggcagcag tgacgactat 660 gggcagctag gggtgcaggc actggagaac caggccactg gtcaggggat ctgcattgct 720 ttcaaggaca tcatgccctt ctctgcccag gtgggcgatg agaggatgca gtgcctcatg 780 cgccacctgg cccaggccgg ggccaccgtc gtggttgttt tttccagccg gcagttggcc 840 agggtgtttt tcgagtccgt ggtgctgacc aacctgactg gcaaggtgtg ggtcgcctca 900 gaagcctggg ccctctccag gcacatcact ggggtgcccg ggatccagcg cattgggatg 960 gtgctgggcg tggccatcca gaagagggct gtccctggcc tgaaggcgtt tgaagaagcc 1020 tatgcccggg cagacaagaa ggcccctagg ccttgccaca agggctcctg gtgcagcagc 1080 aatcagctct gcagagaatg ccaagctttc atggcacaca cgatgcccaa gctcaaagcc 1140 ttctccatga gttctgccta caacgcatac cgggctgtgt atgcggtggc ccatggcctc 1200 caccagctcc tgggctgtgc ctctggagct tgttccaggg gccgagtcta cccctggcag 1260 cttttggagc agatccacaa ggtgcatttc cttctacaca aggacactgt ggcgtttaat 1320 gacaacagag atcccctcag tagctataac ataattgcct gggactggaa tggacccaag 1380 tggaccttca cggtcctcgg ttcctccaca tggtctccag ttcagctaaa cataaatgag 1440 accaaaatcc agtggcacgg aaaggacaac caggtgccta agtctgtgtg ttccagcgac 1500 tgtcttgaag ggcaccagcg agtggttacg ggtttccatc actgctgctt tgagtgtgtg 1560 ccctgtgggg ctgggacctt cctcaacaag agtgacctct acagatgcca gccttgtggg 1620 aaagaagagt gggcacctga gggaagccag acctgcttcc cgcgcactgt ggtgtttttg 1680 gctttgcgtg agcacacctc ttgggtgctg ctggcagcta acacgctgct gctgctgctg 1740 ctgcttggga ctgctggcct gtttgcctgg cacctagaca cccctgtggt gaggtcagca 1800 gggggccgcc tgtgctttct tatgctgggc tccctggcag caggtagtgg cagcctctat 1860 ggcttctttg gggaacccac aaggcctgcg tgcttgctac gccaggccct ctttgccctt 1920 ggtttcacca tcttcctgtc ctgcctgaca gttcgctcat tccaactaat catcatcttc 1980 aagttttcca ccaaggtacc tacattctac cacgcctggg tccaaaacca cggtgctggc 2040 ctgtttgtga tgatcagctc agcggcccag ctgcttatct gtctaacttg gctggtggtg 2100 tggaccccac tgcctgctag ggaataccag cgcttccccc atctggtgat gcttgagtgc 2160 acagagacca actccctggg cttcatactg gccttcctct acaatggcct cctctccatc 2220 agtgcctttg cctgcagcta cctgggtaag gacttgccag agaactacaa cgaggccaaa 2280 tgtgtcacct tcagcctgct cttcaacttc gtgtcctgga tcgccttctt caccacggcc 2340 agcgtctacg acggcaagta cctgcctgcg gccaacatga tggctgggct gagcagcctg 2400 agcagcggct tcggtgggta ttttctgcct aagtgctacg tgatcctctg ccgcccagac 2460 ctcaacagca cagagcactt ccaggcctcc attcaggact acacgaggcg ctgcggctcc 2520 acctga 2526 17 841 PRT Homo sapiens 17 Met Leu Leu Cys Thr Ala Arg Leu Val Gly Leu Gln Leu Leu Ile Ser 1 5 10 15 Cys Cys Trp Ala Phe Ala Cys His Ser Thr Glu Ser Ser Pro Asp Phe 20 25 30 Thr Leu Pro Gly Asp Tyr Leu Leu Ala Gly Leu Phe Pro Leu His Ser 35 40 45 Gly Cys Leu Gln Val Arg His Arg Pro Glu Val Thr Leu Cys Asp Arg 50 55 60 Ser Cys Ser Phe Asn Glu His Gly Tyr His Leu Phe Gln Ala Met Arg 65 70 75 80 Leu Gly Val Glu Glu Ile Asn Asn Ser Thr Ala Leu Leu Pro Asn Ile 85 90 95 Thr Leu Gly Tyr Gln Leu Tyr Asp Val Cys Ser Asp Ser Ala Asn Val 100 105 110 Tyr Ala Thr Leu Arg Val Leu Ser Leu Pro Gly Gln His His Ile Glu 115 120 125 Leu Gln Gly Asp Leu Leu His Tyr Ser Pro Thr Val Leu Ala Val Ile 130 135 140 Gly Pro Asp Ser Thr Asn Arg Ala Ala Thr Thr Ala Ala Leu Leu Ser 145 150 155 160 Pro Phe Leu Val Pro Met Ile Ser Tyr Ala Ala Ser Ser Glu Thr Leu 165 170 175 Ser Val Lys Arg Gln Tyr Pro Ser Phe Leu Arg Thr Ile Pro Asn Asp 180 185 190 Lys Tyr Gln Val Glu Thr Met Val Leu Leu Leu Gln Lys Phe Gly Trp 195 200 205 Thr Trp Ile Ser Leu Val Gly Ser Ser Asp Asp Tyr Gly Gln Leu Gly 210 215 220 Val Gln Ala Leu Glu Asn Gln Ala Thr Gly Gln Gly Ile Cys Ile Ala 225 230 235 240 Phe Lys Asp Ile Met Pro Phe Ser Ala Gln Val Gly Asp Glu Arg Met 245 250 255 Gln Cys Leu Met Arg His Leu Ala Gln Ala Gly Ala Thr Val Val Val 260 265 270 Val Phe Ser Ser Arg Gln Leu Ala Arg Val Phe Phe Glu Ser Val Val 275 280 285 Leu Thr Asn Leu Thr Gly Lys Val Trp Val Ala Ser Glu Ala Trp Ala 290 295 300 Leu Ser Arg His Ile Thr Gly Val Pro Gly Ile Gln Arg Ile Gly Met 305 310 315 320 Val Leu Gly Val Ala Ile Gln Lys Arg Ala Val Pro Gly Leu Lys Ala 325 330 335 Phe Glu Glu Ala Tyr Ala Arg Ala Asp Lys Lys Ala Pro Arg Pro Cys 340 345 350 His Lys Gly Ser Trp Cys Ser Ser Asn Gln Leu Cys Arg Glu Cys Gln 355 360 365 Ala Phe Met Ala His Thr Met Pro Lys Leu Lys Ala Phe Ser Met Ser 370 375 380 Ser Ala Tyr Asn Ala Tyr Arg Ala Val Tyr Ala Val Ala His Gly Leu 385 390 395 400 His Gln Leu Leu Gly Cys Ala Ser Gly Ala Cys Ser Arg Gly Arg Val 405 410 415 Tyr Pro Trp Gln Leu Leu Glu Gln Ile His Lys Val His Phe Leu Leu 420 425 430 His Lys Asp Thr Val Ala Phe Asn Asp Asn Arg Asp Pro Leu Ser Ser 435 440 445 Tyr Asn Ile Ile Ala Trp Asp Trp Asn Gly Pro Lys Trp Thr Phe Thr 450 455 460 Val Leu Gly Ser Ser Thr Trp Ser Pro Val Gln Leu Asn Ile Asn Glu 465 470 475 480 Thr Lys Ile Gln Trp His Gly Lys Asp Asn Gln Val Pro Lys Ser Val 485 490 495 Cys Ser Ser Asp Cys Leu Glu Gly His Gln Arg Val Val Thr Gly Phe 500 505 510 His His Cys Cys Phe Glu Cys Val Pro Cys Gly Ala Gly Thr Phe Leu 515 520 525 Asn Lys Ser Asp Leu Tyr Arg Cys Gln Pro Cys Gly Lys Glu Glu Trp 530 535 540 Ala Pro Glu Gly Ser Gln Thr Cys Phe Pro Arg Thr Val Val Phe Leu 545 550 555 560 Ala Leu Arg Glu His Thr Ser Trp Val Leu Leu Ala Ala Asn Thr Leu 565 570 575 Leu Leu Leu Leu Leu Leu Gly Thr Ala Gly Leu Phe Ala Trp His Leu 580 585 590 Asp Thr Pro Val Val Arg Ser Ala Gly Gly Arg Leu Cys Phe Leu Met 595 600 605 Leu Gly Ser Leu Ala Ala Gly Ser Gly Ser Leu Tyr Gly Phe Phe Gly 610 615 620 Glu Pro Thr Arg Pro Ala Cys Leu Leu Arg Gln Ala Leu Phe Ala Leu 625 630 635 640 Gly Phe Thr Ile Phe Leu Ser Cys Leu Thr Val Arg Ser Phe Gln Leu 645 650 655 Ile Ile Ile Phe Lys Phe Ser Thr Lys Val Pro Thr Phe Tyr His Ala 660 665 670 Trp Val Gln Asn His Gly Ala Gly Leu Phe Val Met Ile Ser Ser Ala 675 680 685 Ala Gln Leu Leu Ile Cys Leu Thr Trp Leu Val Val Trp Thr Pro Leu 690 695 700 Pro Ala Arg Glu Tyr Gln Arg Phe Pro His Leu Val Met Leu Glu Cys 705 710 715 720 Thr Glu Thr Asn Ser Leu Gly Phe Ile Leu Ala Phe Leu Tyr Asn Gly 725 730 735 Leu Leu Ser Ile Ser Ala Phe Ala Cys Ser Tyr Leu Gly Lys Asp Leu 740 745 750 Pro Glu Asn Tyr Asn Glu Ala Lys Cys Val Thr Phe Ser Leu Leu Phe 755 760 765 Asn Phe Val Ser Trp Ile Ala Phe Phe Thr Thr Ala Ser Val Tyr Asp 770 775 780 Gly Lys Tyr Leu Pro Ala Ala Asn Met Met Ala Gly Leu Ser Ser Leu 785 790 795 800 Ser Ser Gly Phe Gly Gly Tyr Phe Leu Pro Lys Cys Tyr Val Ile Leu 805 810 815 Cys Arg Pro Asp Leu Asn Ser Thr Glu His Phe Gln Ala Ser Ile Gln 820 825 830 Asp Tyr Thr Arg Arg Cys Gly Ser Thr 835 840 18 14 PRT Artificial Sequence Description of Artificial Sequence Consensus sequence 18 Xaa Cys Xaa Xaa Arg Xaa Xaa Xaa Phe Leu Xaa Xaa Xaa Glu 1 5 10 19 15 PRT Artificial Sequence Description of Artificial Sequence Consensus sequence 19 Xaa Pro Xaa Xaa Tyr Asn Xaa Ala Xaa Xaa Xaa Thr Xaa Xaa Xaa 1 5 10 15 20 3563 DNA Homo sapiens 20 agcctggcag tggcctcagg cagagtctga cgcgcacaaa ctttcaggcc caggaagcga 60 ggacaccact ggggccccag ggtgtggcaa gtgaggatgg caagggtttt gctaaacaaa 120 tcctctgccc gctccccgcc ccgggctcac tccatgtgag gccccagtcg gggcagccac 180 ctgccgtgcc tgttggaagt tgcctctgcc atgctgggcc ctgctgtcct gggcctcagc 240 ctctgggctc tcctgcaccc tgggacgggg gccccattgt gcctgtcaca gcaacttagg 300 atgaaggggg actacgtgct gggggggctg ttccccctgg gcgaggccga ggaggctggc 360 ctccgcagcc ggacacggcc cagcagccct gtgtgcacca ggtacagagg tgggacggcc 420 tgggtcgggg tcagggtgac caggtctggg gtgctcctga gctggggccg aggtggccat 480 ctgcggttct gtgtggcccc aggttctcct caaacggcct gctctgggca ctggccatga 540 aaatggccgt ggaggagatc aacaacaagt cggatctgct gcccgggctg cgcctgggct 600 acgacctctt tgatacgtgc tcggagcctg tggtggccat gaagcccagc ctcatgttcc 660 tggccaaggc aggcagccgc gacatcgccg cctactgcaa ctacacgcag taccagcccc 720 gtgtgctggc tgtcatcggg ccccactcgt cagagctcgc catggtcacc ggcaagttct 780 tcagcttctt cctcatgccc cagtggggcg ccccccacca tcacccaccc ccaaccaacc 840 cctgccccgt gggagcccct tgtgtcagga gaatgctaca tgcaccccac ccagccctgc 900 cctgggagcc ctgtgtcaga agatgctctt ggccttgcag gtcagctacg gtgctagcat 960 ggagctgctg agcgcccggg agaccttccc ctccttcttc cgcaccgtgc ccagcgaccg 1020 tgtgcagctg acggccgccg cggagctgct gcaggagttc ggctggaact gggtggccgc 1080 cctgggcagc gacgacgagt acggccggca gggcctgagc atcttctcgg ccctggccgc 1140 ggcacgcggc atctgcatcg cgcacgaggg cctggtgccg ctgccccgtg ccgatgactc 1200 gcggctgggg aaggtgcagg acgtcctgca ccaggtgaac cagagcagcg tgcaggtggt 1260 gctgctgttc gcctccgtgc acgccgccca cgccctcttc aactacagca tcagcagcag 1320 gctctcgccc aaggtgtggg tggccagcga ggcctggctg acctctgacc tggtcatggg 1380 gctgcccggc atggcccaga tgggcacggt gcttggcttc ctccagaggg gtgcccagct 1440 gcacgagttc ccccagtacg tgaagacgca cctggccctg gccaccgacc cggccttctg 1500 ctctgccctg ggcgagaggg agcagggtct ggaggaggac gtggtgggcc agcgctgccc 1560 gcagtgtgac tgcatcacgc tgcagaacgt gagcgcaggg ctaaatcacc accagacgtt 1620 ctctgtctac gcagctgtgt atagcgtggc ccaggccctg cacaacactc ttcagtgcaa 1680 cgcctcaggc tgccccgcgc aggaccccgt gaagccctgg caggtgagcc cgggagatgg 1740 gggtgtgctg tcctctgcat gtgcccaggc caccaggcac ggccaccacg cctgagctgg 1800 aggtggctgg cggctcagcc ccgtcccccg cccgcagctc ctggagaaca tgtacaacct 1860 gaccttccac gtgggcgggc tgccgctgcg gttcgacagc agcggaaacg tggacatgga 1920 gtacgacctg aagctgtggg tgtggcaggg ctcagtgccc aggctccacg acgtgggcag 1980 gttcaacggc agcctcagga cagagcgcct gaagatccgc tggcacacgt ctgacaacca 2040 ggtgaggtga gggtgggtgt gccaggcgtg cccgtggtag cccccgcggc agggcgcagc 2100 ctgggggtgg gggccgttcc agtctcccgt gggcatgccc agccgagcag agccagaccc 2160 caggcctgtg cgcagaagcc cgtgtcccgg tgctcgcggc agtgccagga gggccaggtg 2220 cgccgggtca aggggttcca ctcctgctgc tacgactgtg tggactgcga ggcgggcagc 2280 taccggcaaa acccaggtga gccgccttcc cggcaggcgg gggtgggaac gcagcagggg 2340 agggtcctgc caagtcctga ctctgagacc agagcccaca gggtacaaga cgaacaccca 2400 gcgcccttct cctctctcac agacgacatc gcctgcacct tttgtggcca ggatgagtgg 2460 tccccggagc gaagcacacg ctgcttccgc cgcaggtctc ggttcctggc atggggcgag 2520 ccggctgtgc tgctgctgct cctgctgctg agcctggcgc tgggccttgt gctggctgct 2580 ttggggctgt tcgttcacca tcgggacagc ccactggttc aggcctcggg ggggcccctg 2640 gcctgctttg gcctggtgtg cctgggcctg gtctgcctca gcgtcctcct gttccctggc 2700 cagcccagcc ctgcccgatg cctggcccag cagcccttgt cccacctccc gctcacgggc 2760 tgcctgagca cactcttcct gcaggcggcc gagatcttcg tggagtcaga actgcctctg 2820 agctgggcag accggctgag tggctgcctg cgggggccct gggcctggct ggtggtgctg 2880 ctggccatgc tggtggaggt cgcactgtgc acctggtacc tggtggcctt cccgccggag 2940 gtggtgacgg actggcacat gctgcccacg gaggcgctgg tgcactgccg cacacgctcc 3000 tgggtcagct tcggcctagc gcacgccacc aatgccacgc tggcctttct ctgcttcctg 3060 ggcactttcc tggtgcggag ccagccgggc tgctacaacc gtgcccgtgg cctcaccttt 3120 gccatgctgg cctacttcat cacctgggtc tcctttgtgc ccctcctggc caatgtgcag 3180 gtggtcctca ggcccgccgt gcagatgggc gccctcctgc tctgtgtcct gggcatcctg 3240 gctgccttcc acctgcccag gtgttacctg ctcatgcggc agccagggct caacaccccc 3300 gagttcttcc tgggaggggg ccctggggat gcccaaggcc agaatgacgg gaacacagga 3360 aatcagggga aacatgagtg acccaaccct gtgatctcag ccccggtgaa cccagactta 3420 gctgcgatcc cccccaagcc agcaatgacc cgtgtctcgc tacagagacc ctcccgctct 3480 aggttctgac cccaggttgt ctcctgaccc tgaccccaca gtgagcccta ggcctggagc 3540 acgtggacac ccctgtgacc atc 3563 21 839 PRT Homo sapiens 21 Met Gly Pro Arg Ala Lys Thr Ile Cys Ser Leu Phe Phe Leu Leu Trp 1 5 10 15 Val Leu Ala Glu Pro Ala Glu Asn Ser Asp Phe Tyr Leu Pro Gly Asp 20 25 30 Tyr Leu Leu Gly Gly Leu Phe Ser Leu His Ala Asn Met Lys Gly Ile 35 40 45 Val His Leu Asn Phe Leu Gln Val Pro Met Cys Lys Glu Tyr Glu Val 50 55 60 Lys Val Ile Gly Tyr Asn Leu Met Gln Ala Met Arg Phe Ala Val Glu 65 70 75 80 Glu Ile Asn Asn Asp Ser Ser Leu Leu Pro Gly Val Leu Leu Gly Tyr 85 90 95 Glu Ile Val Asp Val Cys Tyr Ile Ser Asn Asn Val Gln Pro Val Leu 100 105 110 Tyr Phe Leu Ala His Glu Asp Asn Leu Leu Pro Ile Gln Glu Asp Tyr 115 120 125 Ser Asn Tyr Ile Ser Arg Val Val Ala Val Ile Gly Pro Asp Asn Ser 130 135 140 Glu Ser Val Met Thr Val Ala Asn Phe Leu Ser Leu Phe Leu Leu Pro 145 150 155 160 Gln Ile Thr Tyr Ser Ala Ile Ser Asp Glu Leu Arg Asp Lys Val Arg 165 170 175 Phe Pro Ala Leu Leu Arg Thr Thr Pro Ser Ala Asp His His Val Glu 180 185 190 Ala Met Val Gln Leu Met Leu His Phe Arg Trp Asn Trp Ile Ile Val 195 200 205 Leu Val Ser Ser Asp Thr Tyr Gly Arg Asp Asn Gly Gln Leu Leu Gly 210 215 220 Glu Arg Val Ala Arg Arg Asp Ile Cys Ile Ala Phe Gln Glu Thr Leu 225 230 235 240 Pro Thr Leu Gln Pro Asn Gln Asn Met Thr Ser Glu Glu Arg Gln Arg 245 250 255 Leu Val Thr Ile Val Asp Lys Leu Gln Gln Ser Thr Ala Arg Val Val 260 265 270 Val Val Phe Ser Pro Asp Leu Thr Leu Tyr His Phe Phe Asn Glu Val 275 280 285 Leu Arg Gln Asn Phe Thr Gly Ala Val Trp Ile Ala Ser Glu Ser Trp 290 295 300 Ala Ile Asp Pro Val Leu His Asn Leu Thr Glu Leu Gly His Leu Gly 305 310 315 320 Thr Phe Leu Gly Ile Thr Ile Gln Ser Val Pro Ile Pro Gly Phe Ser 325 330 335 Glu Phe Arg Glu Trp Gly Pro Gln Ala Gly Pro Pro Pro Leu Ser Arg 340 345 350 Thr Ser Gln Ser Tyr Thr Cys Asn Gln Glu Cys Asp Asn Cys Leu Asn 355 360 365 Ala Thr Leu Ser Phe Asn Thr Ile Leu Arg Leu Ser Gly Glu Arg Val 370 375 380 Val Tyr Ser Val Tyr Ser Ala Val Tyr Ala Val Ala His Ala Leu His 385 390 395 400 Ser Leu Leu Gly Cys Asp Lys Ser Thr Cys Thr Lys Arg Val Val Tyr 405 410 415 Pro Trp Gln Leu Leu Glu Glu Ile Trp Lys Val Asn Phe Thr Leu Leu 420 425 430 Asp His Gln Ile Phe Phe Asp Pro Gln Gly Asp Val Ala Leu His Leu 435 440 445 Glu Ile Val Gln Trp Gln Trp Asp Arg Ser Gln Asn Pro Phe Gln Ser 450 455 460 Val Ala Ser Tyr Tyr Pro Leu Gln Arg Gln Leu Lys Asn Ile Gln Asp 465 470 475 480 Ile Ser Trp His Thr Val Asn Asn Thr Ile Pro Met Ser Met Cys Ser 485 490 495 Lys Arg Cys Gln Ser Gly Gln Lys Lys Lys Pro Val Gly Ile His Val 500 505 510 Cys Cys Phe Glu Cys Ile Asp Cys Leu Pro Gly Thr Phe Leu Asn His 515 520 525 Thr Glu Asp Glu Tyr Glu Cys Gln Ala Cys Pro Asn Asn Glu Trp Ser 530 535 540 Tyr Gln Ser Glu Thr Ser Cys Phe Lys Arg Gln Leu Val Phe Leu Glu 545 550 555 560 Trp His Glu Ala Pro Thr Ile Ala Val Ala Leu Leu Ala Ala Leu Gly 565 570 575 Phe Leu Ser Thr Leu Ala Ile Leu Val Ile Phe Trp Arg His Phe Gln 580 585 590 Thr Pro Ile Val Arg Ser Ala Gly Gly Pro Met Cys Phe Leu Met Leu 595 600 605 Thr Leu Leu Leu Val Ala Tyr Met Val Val Pro Val Tyr Val Gly Pro 610 615 620 Pro Lys Val Ser Thr Cys Leu Cys Arg Gln Ala Leu Phe Pro Leu Cys 625 630 635 640 Phe Thr Ile Cys Ile Ser Cys Ile Ala Val Arg Ser Phe Gln Ile Val 645 650 655 Cys Ala Phe Lys Met Ala Ser Arg Phe Pro Arg Ala Tyr Ser Tyr Trp 660 665 670 Val Arg Tyr Gln Gly Pro Tyr Val Ser Met Ala Phe Ile Thr Val Leu 675 680 685 Lys Met Val Ile Val Val Ile Gly Met Leu Ala Thr Gly Leu Ser Pro 690 695 700 Thr Thr Arg Thr Asp Pro Asp Asp Pro Lys Ile Thr Ile Val Ser Cys 705 710 715 720 Asn Pro Asn Tyr Arg Asn Ser Leu Leu Phe Asn Thr Ser Leu Asp Leu 725 730 735 Leu Leu Ser Val Val Gly Phe Ser Phe Ala Tyr Met Gly Lys Glu Leu 740 745 750 Pro Thr Asn Tyr Asn Glu Ala Lys Phe Ile Thr Leu Ser Met Thr Phe 755 760 765 Tyr Phe Thr Ser Ser Val Ser Leu Cys Thr Phe Met Ser Ala Tyr Ser 770 775 780 Gly Val Leu Val Thr Ile Val Asp Leu Leu Val Thr Val Leu Asn Leu 785 790 795 800 Leu Ala Ile Ser Leu Gly Tyr Phe Gly Pro Lys Cys Tyr Met Ile Leu 805 810 815 Phe Tyr Pro Glu Arg Asn Thr Pro Ala Tyr Phe Asn Ser Met Ile Gln 820 825 830 Gly Tyr Thr Met Arg Arg Asp 835 22 6 PRT Artificial Sequence Description of Artificial Sequence Synthetic PDZIP peptide sequence 22 Ser Val Ser Thr Val Val 1 5 23 2520 DNA Homo sapiens 23 atggggccca gggcaaagac catctgctcc ctgttcttcc tcctatgggt cctggctgag 60 ccggctgaga actcggactt ctacctgcct ggggattacc tcctgggtgg cctcttctcc 120 ctccatgcca acatgaaggg cattgttcac cttaacttcc tgcaggtgcc catgtgcaag 180 gagtatgaag tgaaggtgat aggctacaac ctcatgcagg ccatgcgctt cgcggtggag 240 gagatcaaca atgacagcag cctgctgcct ggtgtgctgc tgggctatga gatcgtggat 300 gtgtgctaca tctccaacaa tgtccagccg gtgctctact tcctggcaca cgaggacaac 360 ctccttccca tccaagagga ctacagtaac tacatttccc gtgtggtggc tgtcattggc 420 cctgacaact ccgagtctgt catgactgtg gccaacttcc tctccctatt tctccttcca 480 cagatcacct acagcgccat cagcgatgag ctgcgagaca aggtgcgctt cccggctttg 540 ctgcgtacca cacccagcgc cgaccaccac gtcgaggcca tggtgcagct gatgctgcac 600 ttccgctgga actggatcat tgtgctggtg agcagcgaca cctatggccg cgacaatggc 660 cagctgcttg gcgagcgcgt ggcccggcgc gacatctgca tcgccttcca ggagacgctg 720 cccacactgc agcccaacca gaacatgacg tcagaggagc gccagcgcct ggtgaccatt 780 gtggacaagc tgcagcagag cacagcgcgc gtcgtggtcg tgttctcgcc cgacctgacc 840 ctgtaccact tcttcaatga ggtgctgcgc cagaacttca cgggcgccgt gtggatcgcc 900 tccgagtcct gggccatcga cccggtcctg cacaacctca cggagctggg ccacttgggc 960 accttcctgg gcatcaccat ccagagcgtg cccatcccgg gcttcagtga gttccgcgag 1020 tggggcccac aggctgggcc gccacccctc agcaggacca gccagagcta tacctgcaac 1080 caggagtgcg acaactgcct gaacgccacc ttgtccttca acaccattct caggctctct 1140 ggggagcgtg tcgtctacag cgtgtactct gcggtctatg ctgtggccca tgccctgcac 1200 agcctcctcg gctgtgacaa aagcacctgc accaagaggg tggtctaccc ctggcagctg 1260 cttgaggaga tctggaaggt caacttcact ctcctggacc accaaatctt cttcgacccg 1320 caaggggacg tggctctgca cttggagatt gtccagtggc aatgggaccg gagccagaat 1380 cccttccaga gcgtcgcctc ctactacccc ctgcagcgac agctgaagaa catccaagac 1440 atctcctggc acaccgtcaa caacacgatc cctatgtcca tgtgttccaa gaggtgccag 1500 tcagggcaaa agaagaagcc tgtgggcatc cacgtctgct gcttcgagtg catcgactgc 1560 cttcccggca ccttcctcaa ccacactgaa gatgaatatg aatgccaggc ctgcccgaat 1620 aacgagtggt cctaccagag tgagacctcc tgcttcaagc ggcagctggt cttcctggaa 1680 tggcatgagg cacccaccat cgctgtggcc ctgctggccg ccctgggctt cctcagcacc 1740 ctggccatcc tggtgatatt ctggaggcac ttccagacac ccatagttcg ctcggctggg 1800 ggccccatgt gcttcctgat gctgacactg ctgctggtgg catacatggt ggtcccggtg 1860 tacgtggggc cgcccaaggt ctccacctgc ctctgccgcc aggccctctt tcccctctgc 1920 ttcacaattt gcatctcctg tatcgccgtg cgttctttcc agatcgtctg cgccttcaag 1980 atggccagcc gcttcccacg cgcctacagc tactgggtcc gctaccaggg gccctacgtc 2040 tctatggcat ttatcacggt actcaaaatg gtcattgtgg taattggcat gctggccacg 2100 ggcctcagtc ccaccacccg tactgacccc gatgacccca agatcacaat tgtctcctgt 2160 aaccccaact accgcaacag cctgctgttc aacaccagcc tggacctgct gctctcagtg 2220 gtgggtttca gcttcgccta catgggcaaa gagctgccca ccaactacaa cgaggccaag 2280 ttcatcaccc tcagcatgac cttctatttc acctcatccg tctccctctg caccttcatg 2340 tctgcctaca gcggggtgct ggtcaccatc gtggacctct tggtcactgt gctcaacctc 2400 ctggccatca gcctgggcta cttcggcccc aagtgctaca tgatcctctt ctacccggag 2460 cgcaacacgc ccgcctactt caacagcatg atccagggct acaccatgag gagggactag 2520 24 6 PRT Artificial Sequence Description of Artificial Sequence Six-His tag 24 His His His His His His 1 5 

What is claimed:
 1. An isolated nucleic acid selected from the group consisting of: (i) a genomic DNA sequence consisting essentially of a nucleic acid sequence coding for a T1R mammalian G protein-coupled receptor polypeptide active in taste signaling, wherein said nucleic acid sequence consists essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and 20; (ii) a genomic DNA sequence consisting essentially of a nucleic acid sequence coding for a T1R mammalian G protein-coupled receptor polypeptide have an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and 21; (iii) a genomic DNA sequence having at least about 50% identity to a nucleic acid sequence coding for a T1R mammalian G protein-coupled receptor polypeptide, wherein said nucleic acid sequence consists essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and 20; a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and (iv) a genomic DNA sequence consisting essentially of a nucleic acid sequence coding for a T1R mammalian G protein-coupled receptor polypeptide having an amino acid sequence that is at least about 40% identical to the amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and 21; (v) a genomic DNA sequence consisting essentially of a sequence coding for a T1R mammalian G protein-coupled receptor polypeptide comprising a consensus sequence selected from the group consisting of SEQ ID NOs 18 and 19, and sequences having at least about 75% identity to SEQ ID NOs 18 or 19; (vi) a cDNA sequence having the same nucleic acid sequence as the T1R mammalian G protein-coupled receptor polypeptide coding region in the genomic DNA sequence selected from the group consisting of SEQ ID NOs 15 and 20; (vii) a cDNA sequence coding for a T1R mammalian G protein-coupled receptor polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and 21; (viii) a cDNA sequence coding for a T1R mammalian G protein-coupled receptor polypeptide comprising a consensus sequence selected from the group consisting of SEQ ID NOs 18 and 19, and sequences having at least about 75% identity to SEQ ID NOs 18 or 19; (ix) a cDNA sequence selected from the group consisting of SEQ ID NOs 3, 13, 16, and 20; (x) a cDNA sequence having at least about 50% sequence identity to the T1R G protein-coupled receptor polypeptide coding region in the genomic DNA sequence selected from the group consisting of SEQ ID NOs 15 and 20; (xi) a cDNA sequence having at least about 50% sequence identity to a sequence encoding a T1R mammalian G protein-coupled receptor polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NOs4, 14, 17, and 21; (xii) a cDNA sequence having at least about 50% identity to a sequence selected from the group consisting of SEQ ID NOs 3, 13, 16, and 20; (xiii) a variant of a nucleotide sequence selected from the group consisting of SEQ ID NOs 3, 13, 15, 16, and 20, containing at least one conservative substitution in a region coding for a T1R G protein-coupled receptor polypeptide active in taste signaling; (xiv) a variant of a nucleotide sequence encoding a T1R G protein-coupled receptor polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and 21, containing at least one conservative substitution in a T1R mammalian G protein-coupled receptor polypeptide coding region; and (xv) a variant of a cDNA sequence selected from the group consisting of SEQ ID NOs 3, 13, 16, and 20, containing at least one conservative substitution.
 2. An isolated genomic DNA molecule consisting essentially of a nucleic acid sequence coding for a mammalian G protein-coupled receptor polypeptide, wherein said nucleic acid sequence consists essential of SEQ ID NO 15 or
 20. 3. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 2. 4. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 2 under stringent hybridization conditions.
 5. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 2 under moderate hybridization conditions.
 6. An isolated fragment of the genomic DNA molecule of claim 2 that is at least about 20 to 30 nucleotide bases in length.
 7. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 2, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 8. The chimeric or fused nucleic acid molecule of claim 7, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 9. The chimeric or fused nucleic acid molecule of claim 7, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 10. The chimeric or fused nucleic acid molecule of claim 9, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 11. The chimeric or fused nucleic acid molecule of claim 7, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 12. An isolated genomic DNA molecule consisting essentially of a nucleic acid sequence coding for a mammalian G protein-coupled receptor having an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and
 21. 13. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 12. 14. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 12 under stringent hybridization conditions.
 15. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 12 under moderate hybridization conditions.
 16. An isolated fragment of the genomic DNA molecule of claim 12 that is at least about 20 to 30 nucleotide bases in length.
 17. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 12, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 18. The chimeric or fused nucleic acid molecule of claim 17, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 19. The chimeric or fused nucleic acid molecule of claim 17, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 20. The chimeric or fused nucleic acid molecule of claim 19, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 21. The chimeric or fused nucleic acid molecule of claim 17, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 22. An isolated genomic DNA molecule consisting essentially of a nucleic acid sequence having at least about 50% identity to a nucleic acid sequence coding for a mammalian G protein-coupled receptor polypeptide, wherein said nucleic acid sequence consists essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and
 20. 23. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 22. 24. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 22 under stringent hybridization conditions.
 25. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 22 under moderate hybridization conditions.
 26. An isolated fragment of the genomic DNA molecule of claim 22 that is at least about 20 to 30 nucleotide bases in length.
 27. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 22, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 28. The chimeric or fused nucleic acid molecule of claim 27, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 29. The chimeric or fused nucleic acid molecule of claim 27, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 30. The chimeric or fused nucleic acid molecule of claim 29, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 31. The chimeric or fused nucleic acid molecule of claim 27, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 32. An isolated genomic DNA molecule consisting essentially of a nucleic acid sequence coding for a mammalian G protein-coupled receptor having an amino acid sequence that is at least about 40% identical to the amino acid sequence selected from the group consisting of SEQ ID NO: 4, 14, 17, and
 21. 33. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 32. 34. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 32 under stringent hybridization conditions.
 35. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 32 under moderate hybridization conditions.
 36. An isolated fragment of the genomic DNA molecule of claim 32 that is at least about 20 to 30 nucleotide bases in length.
 37. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 32, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 38. The chimeric or fused nucleic acid molecule of claim 37, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 39. The chimeric or fused nucleic acid molecule of claim 37, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 40. The chimeric or fused nucleic acid molecule of claim 39, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 41. The chimeric or fused nucleic acid molecule of claim 37, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 42. An isolated cDNA molecule comprising a nucleic acid sequence having the same sequence as the mammalian G protein-coupled receptor polypeptide coding region contained in a genomic DNA sequence consisting essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and
 20. 43. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 42. 44. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 42 under stringent hybridization conditions.
 45. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 42 under moderate hybridization conditions.
 46. An isolated fragment of the genomic DNA molecule of claim 42 that is at least about 20 to 30 nucleotide bases in length.
 47. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 42, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 48. The chimeric or fused nucleic acid molecule of claim 47, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 49. The chimeric or fused nucleic acid molecule of claim 47, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 50. The chimeric or fused nucleic acid molecule of claim 49, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 51. The chimeric or fused nucleic acid molecule of claim 47, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 52. A nucleic acid molecule comprising the isolated cDNA of claim 42 operably linked to a heterologous promoter that is either regulatable or constitutive.
 53. The nucleic acid molecule of claim 52, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 54. An isolated cDNA molecule comprising a nucleic acid sequence coding for a G protein-coupled receptor polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and
 21. 55. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 54. 56. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 54 under stringent hybridization conditions.
 57. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 54 under moderate hybridization conditions.
 58. An isolated fragment of the genomic DNA molecule of claim 54 that is at least about 20 to 30 nucleotide bases in length.
 59. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 54, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 60. The chimeric or fused nucleic acid molecule of claim 59, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 61. The chimeric or fused nucleic acid molecule of claim 59, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 62. The chimeric or fused nucleic acid molecule of claim 61, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 63. The chimeric or fused nucleic acid molecule of claim 59, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 64. A nucleic acid molecule comprising the isolated cDNA of claim 54 operably linked to a heterologous promoter that is either regulatable or constitutive.
 65. The nucleic acid molecule of claim 64, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 66. An isolated cDNA molecule comprising a nucleic acid sequence having at least about 50% sequence identity to the G protein-coupled receptor polypeptide coding region in a genomic DNA sequence consisting essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and
 20. 67. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 66. 68. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 66 under stringent hybridization conditions.
 69. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 66 under moderate hybridization conditions.
 70. An isolated fragment of the genomic DNA molecule of claim 66 that is at least about 20 to 30 nucleotide bases in length.
 71. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 66, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 72. The chimeric or fused nucleic acid molecule of claim 71, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 73. The chimeric or fused nucleic acid molecule of claim 71, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 74. The chimeric or fused nucleic acid molecule of claim 73, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 75. The chimeric or fused nucleic acid molecule of claim 71, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 76. A nucleic acid molecule comprising the isolated cDNA of claim 66 operably linked to a heterologous promoter that is either regulatable or constitutive.
 77. The nucleic acid molecule of claim 76, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 78. An isolated cDNA molecule comprising a nucleic acid sequence having at least about 40% sequence identity to a sequence encoding a mammalian T1R G protein-coupled receptor polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 10, 12, 14, and
 17. 79. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 78. 80. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 78 under stringent hybridization conditions.
 81. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 78 under moderate hybridization conditions.
 82. An isolated fragment of the genomic DNA molecule of claim 78 that is at least about 20 to 30 nucleotide bases in length.
 83. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 78, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 84. The chimeric or fused nucleic acid molecule of claim 83, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 85. The chimeric or fused nucleic acid molecule of claim 83, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 86. The chimeric or fused nucleic acid molecule of claim 85, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 87. The chimeric or fused nucleic acid molecule of claim 83, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 88. A nucleic acid molecule comprising the isolated cDNA of claim 78 operably linked to a heterologous promoter that is either regulatable or constitutive.
 89. The nucleic acid molecule of claim 88, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 90. An isolated variant DNA molecule comprising a nucleotide sequence consisting essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and 20, containing at least one conservative substitution in a region coding for a G protein-coupled receptor active in taste signaling.
 91. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 90. 92. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 90 under stringent hybridization conditions.
 93. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 90 under moderate hybridization conditions.
 94. An isolated fragment of the genomic DNA molecule of claim 90 that is at least about 20 to 30 nucleotide bases in length.
 95. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 90, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 96. The chimeric or fused nucleic acid molecule of claim 95, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 97. The chimeric or fused nucleic acid molecule of claim 95, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 98. The chimeric or fused nucleic acid molecule of claim 97, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 99. The chimeric or fused nucleic acid molecule of claim 95, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 100. A cDNA molecule having the same nucleic acid sequence as the coding region of the variant DNA molecule of claim
 90. 101. A nucleic acid molecule comprising the cDNA of claim 100 operably linked to a heterologous promoter that is either regulatable or constitutive.
 102. The nucleic acid molecule of claim 101, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 103. An isolated variant molecule comprising a nucleotide sequence encoding a polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and 21, containing at least one conservative substitution in a coding region.
 104. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 103. 105. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 103 under stringent hybridization conditions.
 106. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 103 under moderate hybridization conditions.
 107. An isolated fragment of the genomic DNA molecule of claim 103 that is at least about 20 to 30 nucleotide bases in length.
 108. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 103, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 109. The chimeric or fused nucleic acid molecule of claim 108, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 110. The chimeric or fused nucleic acid molecule of claim 108, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 111. The chimeric or fused nucleic acid molecule of claim 110, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 112. The chimeric or fused nucleic acid molecule of claim 108, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 113. A cDNA molecule having the same nucleic acid sequence as the coding region of the variant DNA molecule of claim
 103. 114. A nucleic acid molecule comprising the cDNA molecule of claim 113 operably linked to a heterologous promoter that is either regulatable or constitutive.
 115. The nucleic acid molecule of claim 114, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 116. The isolated nucleic acid molecule of claim 1, wherein said nucleic acid encodes a G protein-coupled receptor polypeptide that is active in taste signaling in rat, mouse, or human.
 117. An expression vector comprising an isolated nucleic acid molecule of claim 1, wherein said vector is selected from the group consisting of mammalian vectors, bacterial plasmids, bacterial phagemids, mammalian viruses and retroviruses, bacteriophage vectors and linear or circular DNA molecules capable of integrating into a host cell genome.
 118. A host cell transfected with at least one of the expression vectors of claim 117, wherein said host cell expresses the encoded G protein-coupled receptor polypeptides on the surface of said host cell.
 119. A nucleic acid array comprising at least about 20 to 30 nucleotides of at least one of the isolated nucleic acid molecules of claim 1, wherein the at least one nucleic acid molecules are linked covalently or noncovalently to a solid phase support.
 120. A method of screening for compounds that activate taste signaling comprising: (i) contacting the host cell of claim 118 with a putative taste activating compound; and (ii) measuring activity from said G protein-coupled receptor polypeptide expressed on the cell surface.
 121. The method of claim 120, wherein said G protein-coupled receptor polypeptide activity is measured by assayed by measuring changes in intracellular Ca²⁺ levels, cAMP, cGMP and IP3, or G protein binding of GTPγS.
 122. The method of claim 120, wherein said host cell is transfected with at least one additional nucleic acid construct encoding a gene involved in taste signaling.
 123. The method of claim 122, wherein said at least one additional gene encodes a G protein involved in taste signal transduction.
 124. The method of claim 123, wherein said G protein is a promiscuous G protein.
 125. A method of screening for compounds that modulate taste signaling transduction comprising: (i) contacting a host cell according to claim 118 with a known taste activating compound and a compound putatively involved in taste transduction modulation; (ii) contacting a host cell according to claim 118 with a known taste activating compound alone; and (iii) comparing the activity from said G protein-coupled receptor polypeptide expressed on the cell surface of the host cell of step (i) with the activity from said G protein-coupled receptor polypeptide expressed on the cell surface of the host cell of step (ii) to identify modulators of taste transduction.
 126. The method of claim 125, wherein said modulatory compounds are selected from the group consisting of activators, inhibitors, stimulators, enhancers, agonists and antagonists.
 127. The method of claim 125, wherein said G protein-coupled receptor polypeptide activity is measured by assayed by measuring changes in intracellular Ca²⁺ levels, cAMP, cGMP and IP3, or G protein binding of GTPγS.
 128. The method of claim 125, wherein said host cell is transfected with at least one additional nucleic acid construct encoding a gene involved in taste signaling.
 129. The method of claim 128, wherein said at least one additional gene encodes a G protein involved in taste signal transduction.
 130. The method of claim 129, wherein said G protein is a promiscuous G protein.
 131. A method of detecting expression of a G protein-coupled receptor polypeptide gene in a cell comprising: (i) contacting said cell with a nucleic acid molecule that hybridizes to the isolated nucleic acid molecule of claim 1 under stringent conditions; and (ii) detecting hybridization in order to detect expression of said G protein-coupled receptor polypeptide gene.
 132. An isolated nucleic acid molecule encoding a G protein-coupled receptor polypeptide active in taste signaling having the nucleotide sequence of SEQ ID NO:
 1. 133. An isolated nucleic acid molecule encoding a G protein-coupled receptor polypeptide active in taste signaling having the nucleotide sequence of SEQ ID NO:
 2. 134. An isolated nucleic acid molecule encoding a G protein-coupled receptor polypeptide active in taste signaling having the nucleotide sequence of SEQ ID NO:
 9. 135. An isolated nucleic acid molecule encoding a G protein-coupled receptor polypeptide active in taste signaling having the nucleotide sequence of SEQ ID NO:
 11. 136. An isolated nucleic acid molecule having the nucleotide sequence of SEQ ID NO:
 3. 137. An isolated nucleic acid molecule having the nucleotide sequence of SEQ ID NO:
 13. 138. An isolated nucleic acid molecule having the nucleotide sequence of SEQ ID NO:
 15. 139. An isolated nucleic acid molecule having the nucleotide sequence of SEQ ID NO:
 16. 140. An isolated nucleic acid molecule encoding the polypeptide having the amino acid sequence of SEQ ID NO:
 4. 141. An isolated nucleic acid molecule encoding the G protein-coupled receptor polypeptide active in taste signaling having the amino acid sequence of SEQ ID NO:
 10. 142. An isolated nucleic acid molecule encoding the G protein-coupled receptor polypeptide active in taste signaling having the amino acid sequence of SEQ ID NO:
 12. 143. An isolated nucleic acid molecule encoding the polypeptide having the amino acid sequence of SEQ ID NO:
 14. 144. An isolated nucleic acid molecule encoding the polypeptide having the amino acid sequence of SEQ ID NO:
 17. 145. An isolated nucleic acid molecule encoding a G protein-coupled receptor polypeptide active in taste signaling comprising the consensus sequence of SEQ ID NO: 18, or a consensus sequence having at least 75% identity to the sequence of SEQ ID NO:
 18. 146. An isolated nucleic acid encoding a G protein-coupled receptor polypeptide active in taste signaling comprising the consensus sequence of SEQ ID NO: 19, or a consensus sequence having at least 75% identity to the sequence of SEQ ID NO:
 19. 147. A genomic DNA amplified by a PCR reaction with at least one degenerate primer having a nucleic acid sequence of SEQ ID NOs 5 or 6, or consisting essentially of a nucleic acid sequence encoding a consensus sequence of SEQ ID NO 18 or 19, wherein said amplified DNA comprises a coding sequence for a G protein-coupled receptor polypeptide active in taste signaling.
 148. A method for isolating a genomic sequence comprising a coding sequence for a G protein-coupled receptor polypeptide active in taste signaling, said method comprising contacting a mammalian genome with at least one degenerate primer having a nucleic acid sequence of SEQ ID NOs 5 or 6, or consisting essentially of a nucleic acid sequence encoding a consensus sequence of SEQ ID NO 18 or 19, and amplifying said genomic sequence comprising said primer sequence in the presence of polymerase, free nucleotides and cofactors.
 149. A method for screening a mammalian genome for a coding sequence for a G protein-coupled receptor active in taste signaling, comprising: (i) contacting said mammalian genome with at least one degenerate primer having a nucleic acid sequence of SEQ ID NOs 5 or 6, or consisting essentially of a nucleic acid sequence encoding a consensus sequence of SEQ ID NO 18 or 19; (ii) amplifying said genomic sequence comprising said at least one primer sequence in the presence of polymerase, free nucleotides and cofactors; and (iii) detecting the presence of an amplified sequence comprising a G protein-coupled receptor polypeptide gene.
 150. Plasmid SAV115 comprising a mouse T1R3 gene.
 151. Plasmid SAV118 comprising a rat T1R3 gene.
 152. An isolated polypeptide selected from the group consisting of: (i) a G protein-coupled receptor polypeptide active in taste signaling encoded by a nucleic acid molecule comprising a nucleic acid sequence selected from the group consisting of SEQ ID NOs 9 and 11, and genomic sequences consisting essentially of SEQ ID NOs 1, and 2; (ii) a G protein-coupled receptor polypeptide encoded by a nucleic acid molecule comprising a nucleic acid sequence selected from the group consisting of SEQ ID NOs 3, 13, 16, and 20, and a genomic sequence consisting essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and 20; (iii) a G protein-coupled receptor polypeptide active in taste signaling comprising an amino acid sequence selected from the group consisting of SEQ ID NOs 10 and 12; (iv) a G protein-coupled receptor polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and 21; (v) a G protein-coupled receptor polypeptide active in taste signaling encoded by a nucleic acid molecule comprising a nucleic acid sequence having at least about 50% identify to a nucleic acid sequence selected from the group consisting of SEQ ID NOs 9 and 11, and genomic sequences consisting essentially of SEQ ID NOs 1, and 2; (vi) a G protein-coupled receptor polypeptide encoded by a nucleic acid molecule comprising a nucleic acid sequence having at least about 50% identify to a nucleic acid sequence selected from the group consisting of SEQ ID NOs 3, 13, 16, and 20, and a genomic sequence consisting essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and 20; (vii) a G protein-coupled receptor polypeptide active in taste signaling comprising an amino acid sequence that is at least about 40% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs 10 and 12; (viii) a G protein-coupled receptor polypeptide comprising an amino acid sequence that is at least about 40% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and 21; (ix) a variant of a G protein-coupled receptor polypeptide active in taste signaling encoded by a nucleic acid molecule comprising a nucleic acid sequence selected from the group consisting of SEQ ID NOs 9 and 11, and genomic sequences consisting essentially of SEQ ID NOs 1, and 2, wherein said variant protein contains at least one conservative substitution relative to the G protein-coupled receptor encoded by said nucleotide sequence; (x) a variant a G protein-coupled receptor polypeptide encoded by a nucleic acid molecule comprising a nucleic acid sequence selected from the group consisting of SEQ ID NOs 3, 13, 16, and 20, and a genomic sequence consisting essentially of a nucleic acid sequence selected from the group consisting of SEQ ID NOs 15 and 20, wherein said variant protein contains at least one conservative substitution relative to the G protein-coupled receptor encoded by said nucleotide sequence; (xi) a variant of a G protein-coupled receptor polypeptide active in taste signaling comprising an amino acid sequence selected from the group consisting of SEQ ID NOs 10 and 12, containing at least one conservative substitution; and (xii) a variant of a G protein-coupled receptor polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NOs 4, 14, 17, and 21, containing at least one conservative substitution.
 153. A fragment of the polypeptide of claim 152, wherein said fragment comprises at least about 5 to 7 amino acids.
 154. The fragment of claim 153, wherein said fragment contains an extracellular domain of a T1R mammalian G protein-coupled receptor polypeptide.
 155. The fragment of claim 154, wherein said extracellular domain interacts with a compound involved in taste activation or modulation.
 156. The fragment of claim 154, wherein said extracellular domain interacts with a protein involved in taste signal transduction.
 157. The fragment of claim 156, wherein said protein involved in taste signal transduction is a G protein subunit.
 158. The fragment of claim 157, wherein said G protein subunit is a promiscuous G protein.
 159. A chimeric or fusion polypeptide comprising at least part of the amino acid sequence of a polypeptide of claim 152, and at least part of a heterologous amino acid sequence.
 160. The chimeric or fusion polypeptide of claim 159, wherein said heterologous sequence is a sequence from a different G protein-coupled receptor.
 161. The chimeric or fusion polypeptide of claim 159, wherein said heterologous sequence is a sequence from green fluorescent protein.
 162. A method of screening one or more compounds for the presence of a compound that activates or modulates taste signaling, comprising contacting said one or more compounds with one or more fragments of one or more polypeptides according to claim 152, wherein the one or more fragments are at least about a 5 to 7 amino acids in length.
 163. A method for screening one or more proteins for the presence of a protein that interacts with a G protein-coupled receptor active in taste signaling, comprising contacting said one or more proteins with one or more fragments of one or more polypeptides according to claim 152, wherein the one or more fragments are at least about a 5 to 7 amino acids in length.
 164. A polypeptide array comprising at least about a 5 to 7 amino acid segment of one or more polypeptides according to claim 152, wherein said one or more polypeptide segments are linked covalently or noncovalently to a solid phase support.
 165. An isolated antibody or antibody fragment that binds with specificity to a polypeptide of claim
 152. 166. An isolated polypeptide having the amino acid sequence of SEQ ID NO:
 4. 167. An isolated polypeptide having the amino acid sequence of SEQ ID NO:
 10. 168. An isolated polypeptide having the amino acid sequence of SEQ ID NO:
 12. 169. An isolated polypeptide having the amino acid sequence of SEQ ID NO:
 14. 170. An isolated polypeptide having the amino acid sequence of SEQ ID NO:
 17. 171. A method for representing the perception of one or more tastes in one or more mammals, comprising the steps of: (i) providing values X₁ to X_(n) representative of the quantitative stimulation of each of n taste receptors of said mammals; and (ii) generating from said values a quantitative representation of taste perception, wherein at least one of said taste receptors is a taste receptor polypeptide having a sequence that is at least about 40% identical to a sequence selected from the group consisting of SEQ ID NOs 4, 10, 12, 14, and
 17. 172. The method of claim 171, wherein said representation constitutes a point or a volume in n-dimensional space.
 173. The method of claim 171, wherein said representation constitutes a graph or a spectrum.
 174. The method of claim 171, wherein said representation constitutes a matrix of quantitative representations.
 175. The method of claim 171, wherein said providing step comprises contacting a plurality of recombinantly produced taste receptors with a test composition and quantitatively measuring the interaction of said composition with said receptors.
 176. A method for predicting the taste perception in a mammal generated by one or more molecules or combinations of molecules comprising the steps of: (i) providing values X₁ to X_(n) representative of the quantitative stimulation of each of n taste receptors of said mammal, for one or more molecules or combinations of molecules yielding known taste perception in a mammal, (ii) generating from said values a quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding known taste perception in a mammal; (iii) providing values X₁ to X_(n) representative of the quantitative stimulation of each of n taste receptors of said mammal, for one or more molecules or combinations of molecules yielding unknown taste perception in a mammal, (iv) generating from said values a quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding unknown taste perception in a mammal; and (v) predicting the taste perception in a mammal generated by one or more molecules or combinations of molecules yielding unknown taste perception in a mammal by comparing the quantitative representation of taste perception in a mammal generated by one or more molecules or combinations of molecules yielding unknown taste perception in a mammal to the quantitative representation of taste perception in a mammal for the one or more molecules or combinations of molecules yielding known taste perception in a mammal, wherein at least one of said taste receptors is a taste receptor polypeptide having a sequence that is at least about 40% identical to a sequence selected from the group consisting of SEQ ID NOs 4, 10, 12, 14, and
 17. 177. A genomic DNA molecule consisting essentially of a nucleic acid sequence coding for a mammalian G protein-coupled receptor polypeptide active in taste signaling comprising a consensus sequence selected from the group consisting of SEQ ID NOs 18 and 19, and sequences having at least about 75% identity to SEQ ID NOs 18 or
 19. 178. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 177. 179. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 177 under stringent hybridization conditions.
 180. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 177 under moderate hybridization conditions.
 181. An isolated fragment of the genomic DNA molecule of claim 177 that is at least about 20 to 30 nucleotide bases in length.
 182. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 177, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 183. The chimeric or fused nucleic acid molecule of claim 182, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 184. The chimeric or fused nucleic acid molecule of claim 182, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 185. The chimeric or fused nucleic acid molecule of claim 184, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 186. The chimeric or fused nucleic acid molecule of claim 182, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 187. A cDNA sequence coding for a mammalian G protein-coupled receptor polypeptide active in taste signaling comprising a consensus sequence selected from the group consisting of SEQ ID NOs 18 and 19, and sequences having at least about 75% identity to SEQ ID NOs 18 or
 19. 188. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 187. 189. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 187 under stringent hybridization conditions.
 190. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 187 under moderate hybridization conditions.
 191. An isolated fragment of the genomic DNA molecule of claim 187 that is at least about 20 to 30 nucleotide bases in length.
 192. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 187, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 193. The chimeric or fused nucleic acid molecule of claim 192, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 194. The chimeric or fused nucleic acid molecule of claim 192, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 195. The chimeric or fused nucleic acid molecule of claim 194, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 196. The chimeric or fused nucleic acid molecule of claim 192, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 197. A nucleic acid molecule comprising the isolated cDNA of claim 187 operably linked to a heterologous promoter that is either regulatable or constitutive.
 198. The nucleic acid molecule of claim 197, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 199. A cDNA molecule comprising a nucleic acid sequence selected from the group consisting of SEQ ID NOs 3, 13, 16, and
 20. 200. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 199. 201. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 199 under stringent hybridization conditions.
 202. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 199 under moderate hybridization conditions.
 203. An isolated fragment of the genomic DNA molecule of claim 199 that is at least about 20 to 30 nucleotide bases in length.
 204. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 199, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 205. The chimeric or fused nucleic acid molecule of claim 204, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 206. The chimeric or fused nucleic acid molecule of claim 204, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 207. The chimeric or fused nucleic acid molecule of claim 206, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 208. The chimeric or fused nucleic acid molecule of claim 204, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 209. A nucleic acid molecule comprising the isolated cDNA of claim 199 operably linked to a heterologous promoter that is either regulatable or constitutive.
 210. The nucleic acid molecule of claim 209, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 211. A cDNA molecule comprising a nucleic acid sequence having at least about 50% identity to a sequence selected from the group consisting of SEQ ID NOs 3, 13, 16, and
 20. 212. An isolated RNA molecule transcribed from the isolated DNA molecule of claim
 211. 213. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 211 under stringent hybridization conditions.
 214. An isolated nucleic acid molecule that hybridizes to the DNA molecule of claim 211 under moderate hybridization conditions.
 215. An isolated fragment of the genomic DNA molecule of claim 211 that is at least about 20 to 30 nucleotide bases in length.
 216. A chimeric or fused nucleic acid molecule, wherein said chimeric or fused nucleic acid molecule comprises at least part of the coding sequence contained in the DNA molecule of claim 211, and at least part of a heterologous coding sequence, wherein transcription of said chimeric or fused nucleic acid molecule results in a single chimeric nucleic acid transcript.
 217. The chimeric or fused nucleic acid molecule of claim 216, wherein said heterologous coding sequence is from a sequence encoding a different G protein-coupled receptor.
 218. The chimeric or fused nucleic acid molecule of claim 216, wherein said heterologous coding sequence is a sequence that facilitates expression of said mammalian G protein-coupled receptor polypeptide on the surface of a cell.
 219. The chimeric or fused nucleic acid molecule of claim 218, wherein said heterologous coding sequence is from a mammalian rhodopsin gene.
 220. The chimeric or fused nucleic acid molecule of claim 216, wherein said heterologous coding sequence is from a gene encoding green fluorescent protein or other detectable marker gene.
 221. A nucleic acid molecule comprising the isolated cDNA of claim 211 operably linked to a heterologous promoter that is either regulatable or constitutive.
 222. The nucleic acid molecule of claim 221, wherein said regulatable promoter is inducible under specific environmental or developmental conditions.
 223. The fragment of claim 153, wherein said fragment includes at least an N-terminal fragment of a G protein-coupled receptor.
 224. The fragment of claim 223, wherein said N-terminal fragment is involved in ligand binding.
 225. The polypeptide fragment of claim 224, wherein said fragment is at least about 100 amino acids in length.
 226. The polypeptide fragment of claim 224, wherein said fragment is at least about 600 amino acids in length.
 227. A biochemical assay for identifying taste stimulus ligands having binding specificity for a G protein-coupled receptor active in taste signaling, comprising: (i) contacting one or more fragments according to claim 224 with one or more putative taste stimulus ligands or a composition comprising one or more putative taste stimulus ligands; and (ii) detecting binding of a taste stimulus ligand having binding specificity for said G protein-coupled receptor active in taste signaling.
 228. The assay of claim 227, wherein binding is detected by displacement of a radiolabeled known binding ligand.
 229. The assay of claim 228, wherein said known binding ligand is an antibody or antibody fragment having binding specificity to said G protein-coupled receptor.
 230. An isolated nucleic acid molecule having the nucleic acid sequence of SEQ ID NO
 20. 231. A chimeric or fusion polypeptide comprising at least an extracellular domain of at least one polypeptide according to claim 152, and at least part of a heterologous amino acid sequence.
 232. The chimeric or fusion polypeptide of claim 231, wherein said heterologous amino acid sequence is a sequence from a different G protein-coupled receptor.
 233. The chimeric or fusion polypeptide of claim 232, wherein said different G protein-coupled receptor is a T1R mammalian G protein-coupled receptor, and said heterologous amino acid sequence includes at least an extracellular domain of said T1R mammalian G protein-coupled receptor.
 234. A biochemical assay for identifying taste stimulus ligands having binding specificity for a G protein-coupled receptor active in taste signaling, comprising: (i) contacting one or more fragments according to claim 224 with a preparation of G proteins and GTPγS, and one or more putative taste stimulus ligands or a composition comprising one or more putative taste stimulus ligands; and (ii) detecting binding of a taste stimulus ligand having binding specificity for said G protein-coupled receptor active in taste signaling by measuring the binding of GTPγS to the G protein. 